fix(gate): defer the screenshot-table close on a capture-pipeline blip instead of treating it as missing evidence

[JSONbored]

Summary

Visual capture failing outright (browserless down, a timeout, a GitHub hiccup fetching a token) looked identical to "capture concluded normally and found no visual evidence" — both left visualCaptureSatisfiedSha unset, so the very next maintenance pass could close a legitimate visual PR purely because an internal service blipped. missing before/after screenshot table was the single most common close reason in the 2026-07-26 ledger, so any false-positive rate here is expensive.

The same gap applied to a preview still building (previewPending) — it already self-heals via a scheduled recapture retry, but never suppressed the close on the very pass that discovered the preview wasn't ready yet.

• visualCaptureRetryPendingSha (new column, migration 0190) marks the exact head SHA a bounded recapture retry is currently scheduled/in-flight for — set only while a retry chance genuinely remains (MAX_PREVIEW_POLL_ATTEMPTS), so the screenshot-table gate's close action defers for exactly as long as that chance exists and never indefinitely. Once the budget is exhausted, the marker is deliberately left unset and the gate falls through to its normal, accurate evaluation on the final attempt.
• The deferral itself is audited (github_app.screenshot_table_close_deferred_capture_retry), not silent.
• A subsequent successful capture for the same head clears the marker (markPullRequestVisualCaptureSatisfied).

Test plan

• npx tsc --noEmit -p tsconfig.json --incremental false — clean
• npm run db:migrations:check / npm run db:schema-drift:check / npm run branding-drift:check — all ok
• npx vitest run test/unit/queue-3.test.ts test/unit/queue-4.test.ts test/unit/queue.test.ts test/unit/queue-2.test.ts test/unit/queue-5.test.ts test/unit/queue-lifecycle-guards.test.ts test/unit/visual-capture.test.ts — 1161 passed
• New regression tests: a capture-pipeline error defers the close and schedules a bounded retry; once the retry budget is exhausted, a still-erroring capture no longer defers the close
• Rebased onto latest main after landing (picked up orb(review): public-surface publish runs outside the per-PR mutex — duplicate gate check-runs and placeholder overwriting a real verdict #9013/fix(review): serialize public-surface publish under the per-PR actuation lock (#9013) #9181's actuation-lock change to the same function, fix(review): finalize CI-stuck silence, post a waiting placeholder, and name every silent AI-review skip #9180, fix(test,docs): resync installation-health fixtures and self-host docs with the #9169 required-events expansion #9203 — auto-merged cleanly, re-verified)

Closes #9030

[superagent-security]

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

[codecov]

Codecov Report

❌ Patch coverage is 72.22222% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.94%. Comparing base (e1ae2f0) to head (b80f932).
⚠️ Report is 4 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/queue/processors.ts	68.75%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9207      +/-   ##
==========================================
- Coverage   93.94%   93.94%   -0.01%     
==========================================
  Files         821      821              
  Lines       81601    81614      +13     
  Branches    24769    24774       +5     
==========================================
+ Hits        76662    76672      +10     
- Misses       3556     3557       +1     
- Partials     1383     1385       +2     

Flag	Coverage Δ
backend	95.21% <72.22%> (-0.01%)	⬇️

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

Files with missing lines	Coverage Δ
src/db/repositories.ts	96.77% <100.00%> (+<0.01%)	⬆️
src/db/schema.ts	73.11% <ø> (ø)
src/types.ts	100.00% <ø> (ø)
src/queue/processors.ts	95.04% <68.75%> (-0.08%)	⬇️