feat(config): add review.auto_merge_summary read-only knobs surface (#2051)

[nickmopen]

Closes #2051 (part of #1959).

Adds review.auto_merge_summary (bool, default off): a read-only collapsible in the unified comment showing which auto-merge conditions currently pass/fail — CI green, gate passing, mergeable-clean, valid linked issue. Surface only — it never changes the merge/close decision. Off ⇒ byte-identical.

What's here

• focus-manifest.ts — autoMergeSummary: boolean | null on FocusManifestReviewConfig (mirrors fixHandoff): normalizeOptionalBoolean parse, default null; round-trip serialize (omitted when null ⇒ byte-identical) + present + EMPTY literals.
• src/review/unified-comment.ts — AutoMergeSummarySignals (already-computed, injected by the host) + pure buildAutoMergeSummaryCollapsible(signals). It renders the conditions table from the injected signals only — no re-derivation, no decision path, no IO. The caller adds it (via the existing extraCollapsibles) only when the knob is on, so off ⇒ nothing added ⇒ byte-identical.
• Docs — review.auto_merge_summary (marked read-only) in both .gittensory.yml.example and config/examples/gittensory.full.yml.

Validation

Ran the full suite locally (npm run test):

Tests  10569 passed | 7 skipped   (0 failed)

Typecheck clean. Covers config absent/true/false round-trip + non-boolean warn, and the render reflecting exactly the injected signal states (all-pass / mixed), deterministic — with an explicit read-only framing assertion (no merge promise/trigger).

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.48%. Comparing base (927001e) to head (4769e4d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3855   +/-   ##
=======================================
  Coverage   93.48%   93.48%           
=======================================
  Files         333      333           
  Lines       33151    33158    +7     
  Branches    12127    12128    +1     
=======================================
+ Hits        30990    30997    +7     
  Misses       1530     1530           
  Partials      631      631           

Files with missing lines	Coverage Δ
src/review/unified-comment.ts	99.52% <100.00%> (+0.01%)	⬆️
src/signals/focus-manifest.ts	99.13% <100.00%> (+<0.01%)	⬆️

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✅ Gittensory review result - approve/merge recommended

_{Review updated: 2026-07-06 18:59:59 UTC}

7 files · 1 AI reviewer · no blockers · readiness 100/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This is a clean, well-scoped config-surface addition that mirrors the existing `fixHandoff` pattern precisely: `autoMergeSummary: boolean | null` is threaded through `EMPTY_MANIFEST`, `emptyManifest`, `parseReviewConfig`, and `reviewConfigToJson` with correct null-omission for byte-identical default behavior. The new `buildAutoMergeSummaryCollapsible` is a pure render function with no IO or decision logic, and test coverage is thorough (absent/true/false round-trip, non-boolean warn, all-pass/mixed render, determinism, read-only framing assertion). The one gap is that the diff never shows the actual call site wiring `buildAutoMergeSummaryCollapsible` into the comment's `extraCollapsibles` gated on `review.autoMergeSummary` — since `unified-comment.ts`'s full content wasn't inlined, I can't confirm whether that invocation exists elsewhere in the file or is deferred to the follow-up work tracked under #1959.

Nits — 5 non-blocking

• Confirm where `buildAutoMergeSummaryCollapsible` is actually invoked and gated on `review.autoMergeSummary` — the diff only adds the builder and the config knob, not the caller wiring; if that's intentionally deferred to feat(review): review.shared_config — operator-level base manifest overlay #1959 follow-up work, say so in the PR description so reviewers don't assume the feature is end-to-end.
• src/signals/focus-manifest.ts uses `r.fixHandoff` (camelCase) for the existing sibling field but `r.auto_merge_summary` (snake_case) for the new one — pre-existing inconsistency, not introduced here, but worth flagging if you ever normalize manifest key casing.
• The issue-number literal `2051` in comments (src/signals/focus-manifest.ts:351) is fine as a doc reference but isn't a runtime magic number needing a constant — no action needed.
• Add a short follow-up note (in the PR body or a TODO near `AutoMergeSummarySignals`) pointing to the exact host call site that will compute and inject the signals, so the read-only/no-decision-path invariant is easy to audit later.
• Consider a small integration test in the unified-comment builder (once wired) asserting the collapsible is appended only when `review.autoMergeSummary` is true and omitted otherwise, matching the byte-identical-off guarantee already tested at the config layer.

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	✅ Linked	#2051
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 142 registered-repo PR(s), 95 merged, 4 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	nickmopen; Gittensor profile; 142 PR(s), 4 issue(s).
Gate result	✅ Passing	No configured blocker found.

Review context

• Author: nickmopen
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: TypeScript
• Official Gittensor activity: 142 PR(s), 4 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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Gittensory approves — the gate is satisfied and CI is green.