docs(agents): add a GEMINI.md pointer to the maintained instructions

[hyperpolymath]

Adds a GEMINI.md pointer file to this repository.

Why. An estate-wide census found a large asymmetry in agent-instruction
files: CLAUDE.md was present almost everywhere, GEMINI.md in a handful of
repositories. Any coding agent that looks for GEMINI.md and does not find one
proceeds with no repository-specific instructions at all.

This file is a pointer, not a second copy of the instructions. Duplicating
guidance across per-agent files guarantees the copies drift. The pointer
redirects to whichever file this repository actually maintains — AGENTS.md
where one exists, otherwise CLAUDE.md — and says to retarget it at
AGENTS.md when one lands.

How this commit was built. The change was made with git plumbing against
origin/<default branch>, not by staging a working tree. The branch contains
exactly one commit adding exactly one file, and carries none of the unrelated
local state present in this checkout. A per-repository assertion required
git diff --name-only <base> <commit> to equal the expected path set exactly,
or the branch was never created.

This PR is opened as a draft on purpose. It is part of a bulk campaign and
is not requesting a merge. Review and merge at your discretion.

🤖 Generated with Claude Code

https://claude.ai/code/session_011eQ7hibx92N7fBDtwgReWk

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: a756ba46-1288-4a6a-a01a-d31f4fb2c216

📥 Commits

Reviewing files that changed from the base of the PR and between 6b728f2 and fa727a7.

📒 Files selected for processing (1)

• GEMINI.md

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

📜 Recent review details

⏰ Context from checks skipped due to timeout. (9)

• GitHub Check: governance / Validate Hypatia Baseline
• GitHub Check: governance / Well-Known (RFC 9116 + RSR)
• GitHub Check: governance / Trusted-base reduction policy
• GitHub Check: governance / Exemption ratchet
• GitHub Check: governance / Security policy checks
• GitHub Check: governance / Actions lockfile verify
• GitHub Check: Rust Tests (macos-latest)
• GitHub Check: Rust Tests (windows-latest)
• GitHub Check: Groove manifest check

⚠️ CI failures not shown inline (2)

GitHub Actions: AffineScript/Deno CI / 0_build.txt: docs(agents): add a GEMINI.md pointer to the maintained instructions

Conclusion: failure

View job details

##[group]Run deno lint
 �[36;1mdeno lint�[0m
 shell: /usr/bin/bash -e {0}
 ##[endgroup]
 �[0m�[1m�[31merror[prefer-const]�[0m: �[0m�[1m`defaultConfig` is never reassigned�[0m
 ##[error] �[0m�[38;5;12m-->�[0m �[0m�[36m/home/runner/work/double-track-browser/double-track-browser/src/utils/Storage.res.js�[0m�[0m�[33m:5:5�[0m

---

GitHub Actions: AffineScript/Deno CI / build: docs(agents): add a GEMINI.md pointer to the maintained instructions

Conclusion: failure

View job details

##[group]Run deno lint
 �[36;1mdeno lint�[0m
 shell: /usr/bin/bash -e {0}
 ##[endgroup]
 �[0m�[1m�[31merror[prefer-const]�[0m: �[0m�[1m`defaultConfig` is never reassigned�[0m
 ##[error] �[0m�[38;5;12m-->�[0m �[0m�[36m/home/runner/work/double-track-browser/double-track-browser/src/utils/Storage.res.js�[0m�[0m�[33m:5:5�[0m

🧰 Additional context used

🧠 Learnings (1)

📓 Common learnings

Learnt from: CR
Repo: hyperpolymath/double-track-browser

Timestamp: 2026-09-08T23:50:50.426Z
Learning: Do not duplicate rules here.

🪛 GitHub Check: Hypatia

GEMINI.md

[warning] 1-1: Hypatia root_hygiene: stale
Stale AI session file -- delete

🔇 Additional comments (1)

GEMINI.md (1)

1-8: LGTM!

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📝 Summary

Summary by CodeRabbit

• Documentation
  • Added guidance for coding agents on where to find repository instructions.
  • Documented the current absence of an AGENTS.md file and the intended future update path.

Walkthrough

Changes

Agent instruction pointer

Layer / File(s)	Summary
Add agent instruction pointer GEMINI.md	Adds guidance to read CLAUDE.md, skip Claude Code-specific tooling, avoid duplicate rules, and retarget the pointer to AGENTS.md when available.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to fa727

This change adds a Gemini instruction pointer to the existing repository guidance and does not alter product behavior or deployment paths. No current merge-blocking risk remains.

Suggested reviewers: metadatastician

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The description clearly explains the addition of the GEMINI.md pointer and its purpose. It is directly related to the changeset.
Title check	✅ Passed	The title is concise, specific, and accurately summarises the addition of the GEMINI.md pointer.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

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_{A rabbit finds the guidance trail
Through CLAUDE.md, clear and plain
No duplicate rules shall grow
To AGENTS.md the pointer goes
And tidy instructions remain}

_{Comment @coderabbitai help to get the list of available commands.}