Introduce Diffy v0.1.0: context-menu git diffing for VS Code

.claude/skills/ci-prep/SKILL.md

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+---
+name: ci-prep
+description: Prepares the current branch for CI by running the exact same steps locally and fixing issues. If CI is already failing, fetches the GH Actions logs first to diagnose. Use before pushing, when CI is red, or when the user says "fix ci".
+argument-hint: "[--failing] [optional job name to focus on]"
+---
+<!-- agent-pmo:74cf183 -->
+
+# CI Prep
+
+Prepare the current state for CI. If CI is already failing, fetch and analyze the logs first.
+
+## Arguments
+
+- `--failing` — Indicates a GitHub Actions run is already failing. When present, you MUST execute **Step 1** before doing anything else.
+- Any other argument is treated as a job name to focus on (but all failures are still reported).
+
+If `--failing` is NOT passed, skip directly to **Step 2**.
+
+## Step 1 — Fetch failed CI logs (only when `--failing`)
+
+You MUST do this before any other work.
+
+```bash
+BRANCH=$(git branch --show-current)
+PR_JSON=$(gh pr list --head "$BRANCH" --state open --json number,title,url --limit 1)
+```
+
+If the JSON array is empty, **stop immediately**:
+> No open PR found for branch `$BRANCH`. Create a PR first.
+
+Otherwise fetch the logs:
+
+```bash
+PR_NUMBER=$(echo "$PR_JSON" | jq -r '.[0].number')
+gh pr checks "$PR_NUMBER"
+RUN_ID=$(gh run list --branch "$BRANCH" --limit 1 --json databaseId --jq '.[0].databaseId')
+gh run view "$RUN_ID"
+gh run view "$RUN_ID" --log-failed
+```
+
+Read **every line** of `--log-failed` output. For each failure note the exact file, line, and error message. If a job name argument was provided, prioritize that job but still report all failures.
+
+## Step 2 — Analyze the CI workflow
+
+1. Find the CI workflow file. Look in `.github/workflows/` for `ci.yml`, `build.yml`, `test.yml`, `checks.yml`, `main.yml`, `pull_request.yml`, or any workflow triggered on `pull_request` or `push`.
+2. Read the workflow file completely. Parse every job and every step.
+3. Extract the ordered list of commands the CI actually runs. In a spec-compliant repo this is `make lint → make test → make build` (REPO-STANDARDS-SPEC [MAKE-TARGETS]), but the actual CI may use `npm`, `cargo`, `dotnet`, raw shell commands, or anything else. Extract what is *actually there*.
+4. Note any environment variables, matrix strategies, or conditional steps that affect execution.
+
+**Do NOT assume the steps are `make lint`, `make test`, `make build`.** The actual CI may run different commands, in a different order. Extract what the CI *actually does*. If you find extra targets beyond the 7 in [MAKE-TARGETS] (e.g. `make fmt-check`, `make coverage-check`), flag them in your final report — they should be consolidated by the agent-pmo skill.
+
+### Release workflow blocker scan
+
+If `.github/workflows/release.yml` exists, scan it before broad local CI. These are critical blockers
+and must be fixed before release work is considered CI-ready:
+
+- Tag-triggered jobs checking out `ref: main` instead of the tagged SHA.
+- Any `git commit`, `git push`, branch mutation, or tag mutation during release.
+- Version bump commits after the tag already exists.
+- Ad hoc `sed` version stamping of structured files instead of a first-class stamper/build input.
+- Missing tests that pass a test version into the same stamper used by release.
+- Native VSIX releases without Node `22.x`, `npx vsce package --target <vsceTarget>`, one VSIX per
+  target, target-suffixed filenames, and package-content verification.
+- VS Code native-binary activation that reads or mutates PATH, uses package-manager/global installs
+  as normal startup sources, or copies bundled VSIX binaries after install.
+
+## Step 3 — Run each CI step locally, in order
+
+Work through failures in this priority order:
+
+1. **Formatting** — run auto-formatters first to clear noise
+2. **Compilation errors** — must compile before lint/test
+3. **Lint violations** — fix the code pattern
+4. **Runtime / test failures** — fix source code to satisfy the test
+
+For each command extracted from the CI workflow:
+
+1. Run the command exactly as CI would run it (adjusting only for local environment differences like not needing `actions/checkout`).
+2. If the step fails, **stop and fix the issues** before continuing to the next step.
+3. After fixing, re-run the same step to confirm it passes.
+4. Move to the next step only after the current one succeeds.
+
+### Hard constraints
+
+- **NEVER modify test files** — fix the source code, not the tests
+- **NEVER add suppressions** (`// eslint-disable`, `// @ts-ignore`, `// @ts-nocheck`)
+- **NEVER use `any` in TypeScript** to silence type errors
+- **NEVER delete or ignore failing tests**
+- **NEVER remove assertions**
+
+If stuck on the same failure after 5 attempts, ask the user for help.
+
+## Step 4 — Report
+
+- List every step that was run and its result (pass/fail/fixed).
+- If any step could not be fixed, report what failed and why.
+- Confirm whether the branch is ready to push.
+
+## Step 5 — Remote CI follow-up (only when `--failing`)
+
+Once all CI steps pass locally:
+
+1. Report the local fixes and exact commands that now pass.
+2. Do not commit or push. The user owns source-control writes.
+3. If the user pushes, monitor the new run until completion or failure.
+4. Upon failure, go back to Step 1.
+
+## Rules
+
+- **Always read the CI workflow first.** Never assume what commands CI runs.
+- Do not commit or push from this skill.
+- Fix issues found in each step before moving to the next
+- Never skip steps or suppress errors
+- If the CI workflow has multiple jobs, run all of them (respecting dependency order)
+- Skip steps that are CI-infrastructure-only (checkout, setup-node/python/rust actions, cache steps, artifact uploads) — focus on the actual build/test/lint commands
+
+## Success criteria
+
+- Every command that CI runs has been executed locally and passed
+- All fixes are applied to the working tree
+- The CI passes successfully (if you are correcting and existing failure)

.claude/skills/code-dedup/SKILL.md

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+---
+name: code-dedup
+description: Searches for duplicate code, duplicate tests, and dead code, then safely merges or removes them. Use when the user says "deduplicate", "find duplicates", "remove dead code", "DRY up", or "code dedup". Requires test coverage — refuses to touch untested code.
+---
+<!-- agent-pmo:74cf183 -->
+
+# Code Dedup
+
+Carefully search for duplicate code, duplicate tests, and dead code across the Diffy repo. Merge duplicates and delete dead code — but only when test coverage proves the change is safe.
+
+## Prerequisites — hard gate
+
+Before touching ANY code, verify these conditions. If any fail, stop and report why.
+
+1. Run `make test` — all tests must pass. If tests fail, stop. Do not dedup a broken codebase.
+2. Run `make test` — tests are fail-fast AND enforce the coverage threshold from `coverage-thresholds.json`. If anything fails, stop and fix it before deduping.
+3. Verify the project uses **static typing**. TypeScript with `tsconfig.json` `"strict": true` is required (which Diffy enforces — see CLAUDE.md). If `strict` is off, STOP and refuse.
+
+## Steps
+
+Copy this checklist and track progress:
+
+```
+Dedup Progress:
+- [ ] Step 1: Prerequisites passed (tests green, coverage met, strict TS)
+- [ ] Step 2: Dead code scan complete
+- [ ] Step 3: Duplicate code scan complete
+- [ ] Step 4: Duplicate test scan complete
+- [ ] Step 5: Changes applied
+- [ ] Step 6: Verification passed (tests green, coverage stable)
+```
+
+### Step 1 — Inventory test coverage
+
+Before deciding what to touch, understand what is tested.
+
+1. Run `make test` to confirm green baseline. `make test` is fail-fast AND enforces the coverage threshold from `coverage-thresholds.json` (REPO-STANDARDS-SPEC [TEST-RULES], [COVERAGE-THRESHOLDS-JSON]). It exits non-zero on any test failure OR coverage shortfall.
+2. Note the current coverage percentage — this is the floor. It must not drop.
+3. Identify which files/modules have coverage and which do not. Only files WITH coverage are candidates for dedup.
+
+### Step 2 — Scan for dead code
+
+Search for code that is never called, never imported, never referenced.
+
+1. Look for unused exports, unused functions, unused classes, unused variables.
+2. Check TypeScript: `noUnusedLocals`/`noUnusedParameters` are already enabled in Diffy's `tsconfig.json`. Look for unexported helpers with zero references.
+3. For each candidate: **grep the entire codebase** (including `src/test/`, `package.json` `contributes`, `scripts/`, configs) for references. Only mark as dead if truly zero references.
+4. List all dead code found with file paths and line numbers. Do NOT delete yet.
+
+### Step 3 — Scan for duplicate code
+
+Search for code blocks that do the same thing in multiple places.
+
+1. Look for functions/methods with identical or near-identical logic.
+2. Look for copy-pasted blocks (same structure, maybe different variable names).
+3. Look for multiple implementations of the same algorithm or pattern.
+4. Check across module boundaries — Diffy's layered architecture (`src/git/`, `src/ui/`, `src/providers/`, `src/commands/`) is a natural place for accidental duplication.
+5. For each duplicate pair: note both locations, what they do, and how they differ (if at all).
+6. List all duplicates found. Do NOT merge yet.
+
+### Step 4 — Scan for duplicate tests
+
+Search for tests that verify the same behavior.
+
+1. Look for test functions with identical assertions against the same code paths.
+2. Look for test fixtures/helpers that are duplicated across `src/test/unit/` and `src/test/suite/`.
+3. Look for E2E tests that fully cover what a unit test also covers (per CLAUDE.md, E2E is preferred — keep the E2E, mark the unit test as redundant only if E2E genuinely subsumes its coverage).
+4. List all duplicate tests found. Do NOT delete yet.
+
+### Step 5 — Apply changes (one at a time)
+
+For each change, follow this cycle: **change → test → verify coverage → continue or revert**.
+
+#### 5a. Remove dead code
+- Delete dead code identified in Step 2
+- After each deletion: run `make test` (fail-fast + coverage + threshold all in one)
+- If `make test` exits non-zero (test failure OR coverage drop): **revert immediately** and investigate
+- Dead code removal should never break tests or drop coverage
+
+#### 5b. Merge duplicate code
+- For each duplicate pair: extract the shared logic into a single function/module
+- Update all call sites to use the shared version
+- After each merge: run `make test`
+- If tests fail: **revert immediately**. The duplicates may have subtle differences you missed.
+- If coverage drops: the shared code must have equivalent test coverage. Add tests if needed before proceeding.
+
+#### 5c. Remove duplicate tests
+- Delete the redundant test (keep the more thorough one)
+- After each deletion: run `make test`
+- If coverage drops below threshold, `make test` exits non-zero — **revert immediately**. The "duplicate" test was covering something the other wasn't.
+
+### Step 6 — Final verification
+
+1. Run `make lint` — ESLint + tsc --noEmit must pass clean.
+2. Run `make test` — tests must pass AND coverage must remain ≥ the baseline from Step 1.
+3. Report: what was removed, what was merged, final coverage vs baseline.
+
+(Only the 7 standard targets exist — `make lint` and `make test` cover linting and coverage checks respectively.)
+
+## Rules
+
+- **No test coverage = do not touch.** If a file has no tests covering it, leave it alone entirely. You cannot safely dedup what you cannot verify.
+- **Coverage must not drop.** If removing or merging code causes coverage to decrease, revert and investigate. The coverage floor from Step 1 is sacred.
+- **Strict TypeScript only.** Diffy enforces `strict: true`. If that ever changes, refuse to dedup until it's re-enabled.
+- **One change at a time.** Make one dedup change, run tests, verify coverage. Never batch multiple dedup changes before testing.
+- **When in doubt, leave it.** If two code blocks look similar but you're not 100% sure they're functionally identical, leave both. False dedup is worse than duplication.
+- **Preserve public API surface.** Do not change exported function signatures, command IDs, URI scheme, or `package.json` `contributes` keys that the extension exposes.
+- **Three similar lines is fine.** Do not create abstractions for trivial duplication. Per CLAUDE.md: three similar lines is better than a premature abstraction. Only dedup when the shared logic is substantial (>10 lines) or when there are 3+ copies.

.claude/skills/fix-bug/SKILL.md

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+---
+name: fix-bug
+description: Fix a bug using test-driven development. Use when the user reports a bug, describes unexpected behavior, wants to fix a defect, or says something is broken. Enforces a strict test-first workflow where a failing test must be written and verified before any fix is attempted.
+argument-hint: "[bug description]"
+allowed-tools: Read, Grep, Glob, Edit, Write, Bash
+---
+<!-- agent-pmo:74cf183 -->
+
+# Bug Fix Skill — Test-First Workflow
+
+You MUST follow this exact workflow. Do NOT skip steps. Do NOT fix the bug before writing a failing test.
+
+## Step 1: Understand the Bug
+
+- Read the bug description: $ARGUMENTS
+- Investigate the codebase to understand the relevant code
+- Identify the root cause (or narrow down candidates)
+- Summarize your understanding of the bug to the user before proceeding
+
+## Step 2: Write a Failing Test
+
+- Write a test that **directly exercises the buggy behavior**
+- The test must assert the **correct/expected** behavior — so it FAILS against the current broken code
+- The test name should clearly describe the bug (e.g., `test_orange_color_not_applied_to_head`)
+- Use the project's existing test framework and conventions (Diffy uses mocha for unit and `@vscode/test-electron` for E2E — pick the right tier per CLAUDE.md)
+
+## Step 3: Run the Test — Confirm It FAILS
+
+- Run ONLY the new test (not the full suite)
+- **Verify the test FAILS** and that it fails **because of the bug**, not for some other reason (typo, import error, wrong selector, etc.)
+- If the test passes: your test does not capture the bug. Go back to Step 2
+- If the test fails for the wrong reason: fix the test, not the code. Go back to Step 2
+- **Repeat until the test fails specifically because of the bug**
+
+## Step 4: Show Failure to User
+
+- Show the user the test code and the failure output
+- Explicitly ask: "This test fails because of the bug. Can you confirm this captures the issue before I fix it?"
+- **STOP and WAIT for user acknowledgment before proceeding**
+- Do NOT continue to Step 5 until the user confirms
+
+## Step 5: Fix the Bug
+
+- Make the **minimum change** needed to fix the bug
+- Do not refactor, clean up, or "improve" surrounding code
+- Do not change the test
+
+## Step 6: Run the Test — Confirm It PASSES
+
+- Run the new test again
+- **Verify it PASSES**
+- If it fails: go back to Step 5 and adjust the fix
+- **Repeat until the test passes**
+
+## Step 7: Run the Full Test Suite
+
+- Run `make test` to make sure nothing else broke (fail-fast + coverage threshold per CLAUDE.md)
+- If other tests fail: fix the regression without breaking the new test
+- Report the final result to the user
+
+## Rules
+
+- NEVER fix the bug before the failing test is written and confirmed
+- NEVER skip asking the user to acknowledge the test failure
+- NEVER modify the test to make it pass — modify the source code
+- If you cannot write a test for the bug, explain why and ask the user how to proceed
+- Keep the fix minimal — one bug, one fix, one test