fix(engine): re-validate screenshot matrix evidence on re-push (#8866)

[andriypolanski]

PR body

Summary

• Closes fix(engine): screenshot-table matrix mode has no re-push staleness guard despite doc comment claiming otherwise #8866
• Extracts a shared evidenceFreshnessForHead helper and runs it from both presence and matrix branches of evaluateScreenshotTableGate, so matrix mode persists/reuses the same (headSha, evidenceFingerprint) checkpoint presence mode already used.
• A complete matrix that satisfied push feat(docs): add install site and mcp diagnostics #1 now re-violates on push chore(release): prepare public gittensory launch #2 when the body (image URLs) never changed; re-affirming with new image URLs still passes.
• Adds unit coverage plus a queue-3 regression mirroring the existing presence-mode stale-push test.

Scope

• The PR title follows type(scope): short summary Conventional Commit format, for example fix(api): restore profile access checks.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked a currently open issue this PR resolves (e.g. Closes #123) — a linked open issue is required for every contributor PR.

Validation

• git diff --check
• npx vitest run test/unit/screenshot-table-gate-engine.test.ts test/unit/screenshot-table-gate.test.ts -t "8866|matrix mode" — passed
• npx vitest run test/unit/queue-3.test.ts -t "stale-screenshot-table-fix|#8866" — 2 passed
• CI-scoped Codecov simulation: npx diff-cover coverage/lcov.info --compare-branch=origin/main --include-untracked — 100% patch lines
• npm run actionlint
• npm run typecheck
• npm run test:coverage
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

If any required check was skipped, explain why:

Narrow engine gate staleness fix; full test:ci left for the opener before push. Targeted engine + queue-3 tests cover the matrix stale/re-affirm/no-headSha paths.

Notes for reviewers / gate

• No secrets, wallets, hotkeys, trust scores, or reward values.
• Does not touch site/, CNAME, **/lovable/**, or CHANGELOG.md.
• No UI Evidence (backend-only).

[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 93.88%. Comparing base (8444812) to head (0baf45a).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9038      +/-   ##
==========================================
- Coverage   93.88%   93.88%   -0.01%     
==========================================
  Files         809      809              
  Lines       80553    80560       +7     
  Branches    24436    24441       +5     
==========================================
+ Hits        75628    75631       +3     
  Misses       3560     3560              
- Partials     1365     1369       +4     

Flag	Coverage Δ
backend	95.16% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...oopover-engine/src/review/screenshot-table-gate.ts	100.00% <100.00%> (ø)
src/queue/processors.ts	95.72% <ø> (ø)

... and 1 file with indirect coverage changes

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Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-26 16:35:07 UTC}

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

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This extracts the presence-mode staleness check (headSha/evidenceFingerprint correlation, originally #stale-screenshot-table-fix) into a shared `evidenceFreshnessForHead` helper and wires it into matrix mode too, closing the gap where a complete viewport/theme matrix satisfied on push #1 kept silently passing on later pushes with unchanged evidence. The refactor is a faithful behavior-preserving extraction for presence mode (the extracted logic is byte-identical to what was inlined before) and correctly reuses the same `presenceModeSatisfiedState` persistence/consumption path in `processors.ts` and `screenshotTablePresenceSatisfied` DB field for matrix mode, so no new schema/wiring is needed. Tests cover stale-reuse, re-affirm-with-new-URLs, and no-headSha-degrades-gracefully paths for matrix mode, mirroring the existing presence-mode test shapes, and the queue-3 integration test drives the real close path end-to-end across two pushes.

Nits — 5 non-blocking

• The reused field name `presenceModeSatisfiedState`/`ScreenshotTablePresenceEvidence` now also represents matrix-mode checkpoints; a rename (e.g. `evidenceSatisfiedState`) would reduce confusion for future readers, though this is purely cosmetic since the JSDoc above it was updated to clarify the dual use.
• screenshot-table-gate.ts has grown to ~463 lines per the external size-smell note; if this area keeps accumulating shared logic it may be worth splitting the matrix/presence evaluators into a submodule.
• validate-code failed with no detail provided, and per BASE BRANCH STATUS this branch is 9 commits behind default — worth rebasing to rule out a stale-branch cause before assuming a real defect.
• Consider renaming `presenceModeSatisfiedState` to something mode-neutral now that matrix mode also populates/consumes it, to avoid future readers assuming it's presence-only despite the updated comment.
• Rebase onto the latest default branch to see if the undetailed validate-code failure clears, given the 9-commit drift noted in BASE BRANCH STATUS.

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ✅ Gate result — Passing (No configured blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#8866
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: 200 registered-repo PR(s), 126 merged, 22 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	andriypolanski; Gittensor profile; 200 PR(s), 22 issue(s).
Improvement	✅ Minor	risk: clean · value: minor · LLM: moderate

Linked issue satisfaction

Addressed
The diff extracts a shared evidenceFreshnessForHead helper and wires it into the matrix branch of evaluateScreenshotTableGate exactly as requested, updates the doc comments to match reality, and adds both unit tests (engine-level) and a queue-3 regression test mirroring the presence-mode staleness test for matrix mode.

Review context

• Author: andriypolanski
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: Python, TypeScript, Rust, Cuda, JavaScript, Kotlin, MDX, Scala
• Official Gittensor activity: 200 PR(s), 22 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.

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

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