feat(cli): explicit validation modes --mode basic|strict|release (#52)

[SollanSystems]

Closes #52. Slice S2 of the Phase 0/1 roadmap run (SPEC criterion 3).

What

• loop doctor|validate|verify --mode basic|strict|release (default = unchanged auto-detect; basic = the structural fallback made explicit and deterministic even when jsonschema is installed).
• strict/release require real JSON-Schema validation and fail loud — new ValidationModeError (RuntimeError subclass), CLI exit 2, stderr names jsonschema and the --mode basic escape hatch, no traceback — instead of silently downgrading.
• release ≡ strict today with reserved semantics, pinned by a tripwire test so future divergence is a conscious diff.
• Reports gain requested_mode (auto|basic|strict|release) alongside the untouched internal validation_mode key; VALIDATION_MODES re-exported from the package root (ValidationModeError deliberately not, per the EmitError precedent).
• CI Quickstart smoke now runs doctor --mode release; new scripts/test_ci_release_mode.py pins the wiring.

Evidence (governed Claudex lane: gpt-5.6-terra worker, deterministic argv gates outside the worker, fresh claude-sonnet-5 review, Fable governance)

• Scope gate: exactly 8 allowed files; both existing test files purely additive (zero removed lines).
• Deterministic gates 7/7: extras suite 544 passed / 14 skipped (base 528/14, +16 new tests, zero regressions); pyyaml-only suite 526 passed / 32 skipped (base 513/29) — the jsonschema-absent env genuinely exercises the fail-loud branch; frontmatter + self_eval; release/basic doctor smokes; py_compile; negative probes (strict-without-jsonschema / bogus / valueless --mode → exit 2, stderr-shaped, no stdout, no traceback).
• Independent review: PASS; reviewer arithmetic cross-check of new-test counts matches gate evidence exactly in both env shapes.
• One verifier-directed repair (attempt 2/2): a new CLI test was not environment-aware (asserted release exits 0 with jsonschema absent); fixed to assert the fail-loud contract in that env. Codex sessions: 019f5c50-b7ab-71d0-a15c-ccdb0afd94bb (a1), 019f5c5b-d58e-7150-bc04-5be8216b46a6 (a2); receipts cx_s2_modes_a1 (repair_requested), cx_s2_modes_a2 (accepted).

Test plan

• Full suite, jsonschema present: 544/14
• Full suite, pyyaml-only: 526/32 (no regressions vs 513/29 baseline)
• Fail-loud negative probes outside pytest
• CI runs release mode on all matrix legs (jsonschema installed unconditionally)

https://claude.ai/code/session_01EJ8zA8Cbi4o2amawpj8bZW

[Copilot]

Pull request overview

This PR makes contract validation strength explicit and deterministic for the CLI “doctor-family” commands by adding --mode basic|strict|release, while keeping the default behavior (auto) unchanged for backward compatibility. It also adds reporting that distinguishes the caller-requested mode from the internally selected validation branch.

Changes:

• Add public validation modes (basic|strict|release) with “fail loud” behavior for strict/release when jsonschema is unavailable, plus requested_mode in validation reports.
• Extend the CLI (doctor|validate|verify) to parse --mode, return exit code 2 on mode/availability errors, and avoid tracebacks for these user-facing failures.
• Update CI quickstart smoke to run doctor --mode release and add tests that pin the CLI/API behavior and CI wiring.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
scripts/test_loop_contract_core.py	Adds API-level tests for VALIDATION_MODES, requested_mode, and strict/release behavior.
scripts/test_loop_cli.py	Adds end-to-end CLI subprocess tests for --mode behavior, exit codes, and stderr/stdout shaping.
scripts/test_ci_release_mode.py	Adds a CI workflow “wiring contract” test to pin release-mode usage in the smoke step.
README.md	Documents the new requested_mode report field and the --mode semantics.
loop/contract.py	Implements mode resolution, introduces ValidationModeError, threads mode through validate_contract/doctor_report, and reports requested_mode.
loop/main.py	Parses --mode for doctor/validate/verify, maps mode errors to exit 2, updates help text.
loop/init.py	Re-exports VALIDATION_MODES from the package root.
.github/workflows/ci.yml	Updates the Quickstart smoke test to run doctor --mode release.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.