feat(review): add a visible caption under each Visual/Scroll preview thumbnail

[JSONbored]

Summary

• The screenshot-table contract this bot enforces on contributors (see e.g. .claude/skills/metagraphed/SKILL.md's Phase B2 in JSONbored/metagraphed) requires "each image is a clickable thumbnail... with a one-line caption underneath." The bot's own Visual preview / Scroll preview tables never rendered one — the route/viewport/theme label existed only as an invisible alt attribute.
• Adds a <br><sub>label</sub> line (the same label already used for alt) after each thumbnail, inside the same table cell (a literal newline would break the GFM table row). Purely additive to both buildBeforeAfterCollapsible and buildScrollPreviewCollapsible's cell() builders — every existing assertion about the <a>/<img> markup still matches unchanged.

This is one of two fixes for #6324; the image-downscaling half (the "before images are massive" file-size complaint) is a larger, separate change and will land in its own follow-up PR — this one alone doesn't fully resolve #6324, so it doesn't carry a closing keyword.

Test plan

• All 25 pre-existing test/unit/visual-collapsible.test.ts assertions pass unchanged (the caption is purely additive)
• 3 new tests: the caption renders visibly for both builders, and a dash (missing) cell emits no stray caption markup
• Confirmed no other test file asserts on this markup shape
• npm run typecheck clean
• Full local npm run test:ci gate green

[superagent-security]

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

[loopover-orb]

Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-16 02:57:46 UTC}

2 files · 1 AI reviewer · no blockers · readiness 88/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This adds a visible `<br><sub>label</sub>` caption under each thumbnail in both `buildBeforeAfterCollapsible` and `buildScrollPreviewCollapsible`, reusing the existing `attr()`-escaped label already used for the `alt` attribute, and is purely additive so pre-existing assertions on the `<a>`/`<img>` markup still match. The change correctly links to open issue #6324 (partial fix, explicitly not closing it), and the three new tests verify the visible caption renders for both builders and that the dash/missing case emits no stray `<br><sub>`.

Nits — 5 non-blocking

• The doc comment in unified-comment-bridge.ts:458 is quite long (5 lines) for a one-line stylistic addition; could be trimmed to 1-2 lines since the rationale is already in the PR description.
• Consider a shared helper for the `cell()` builder logic since it's now duplicated nearly identically across both functions, though this pre-dates this diff.
• Consider extracting the common `<a>...<img>...</a><br><sub>...</sub>` cell template into a shared helper used by both `buildBeforeAfterCollapsible` and `buildScrollPreviewCollapsible` to avoid future drift between the two near-identical `cell()` functions.
• test/unit/visual-collapsible.test.ts's new tests are well-scoped; consider also asserting the exact ordering (`<img>` before `<br><sub>`) rather than only substring containment, though current assertions are adequate.
• PR author also opened the linked issue — Link an issue that was opened by a different contributor, or provide a rationale for why this self-authored issue represents genuine discovery work.

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	#6324
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	❌ 8/20	High 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: 42 registered-repo PR(s), 34 merged, 443 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	JSONbored; Gittensor profile; 42 PR(s), 443 issue(s).
Improvement	✅ Minor	risk: clean · value: minor · LLM: moderate

Linked issue satisfaction

Partially addressed
The PR adds the visible one-line caption under each thumbnail (via <br>_label) matching the contributor contract, with tests covering desktop/mobile/scroll cells and confirming missing-cell markup is unaffected, but it explicitly does not address the image downscaling deliverable (real ~360-720px encode, separate thumb key, full-size link, hosted-mode parity) which is the other major hal

Review context

• Author: JSONbored
• Role context: owner (maintainer lane)
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 42 PR(s), 443 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Start here: Treat this as maintainer-lane context rather than normal contributor-lane activity.
• Then work through the remaining 2 steps in the Signals table above.

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-orb]

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.60%. Comparing base (f642d91) to head (29db944).
⚠️ Report is 32 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6341   +/-   ##
=======================================
  Coverage   95.60%   95.60%           
=======================================
  Files         597      597           
  Lines       47170    47170           
  Branches    15016    15016           
=======================================
  Hits        45098    45098           
  Misses       1290     1290           
  Partials      782      782           

Flag	Coverage Δ
shard-1	43.98% <50.00%> (-0.18%)	⬇️
shard-2	36.78% <0.00%> (+0.39%)	⬆️
shard-3	32.30% <50.00%> (-0.15%)	⬇️
shard-4	34.40% <50.00%> (-0.17%)	⬇️
shard-5	31.80% <100.00%> (+0.02%)	⬆️
shard-6	45.29% <50.00%> (+0.44%)	⬆️

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

Files with missing lines	Coverage Δ
src/review/unified-comment-bridge.ts	99.60% <100.00%> (ø)