fix(review): paginate preview-url.ts's PR-comment and check-run GitHub reads

[xfodev]

Summary

Fixes #7450: src/review/visual/preview-url.ts's findPreviewUrlFromPrComments and getPreviewBuildState each fetched exactly one per_page=100 page (no page param, no Link header check) of /issues/{prNumber}/comments and /commits/{sha}/check-runs. On a PR with >100 discussion comments or a commit with >100 check-runs, the Cloudflare Workers Builds bot's preview-URL comment / check-run can land on page 2+, and either function then silently returned null / "absent" as if it genuinely didn't exist — a truncated page-1 response is indistinguishable from an empty one.

Both now walk the response's Link: rel="next" header, bounded to PREVIEW_LIST_MAX_PAGES = 10 — mirroring this repo's existing precedents (src/github/backfill.ts's githubPaginatedList/PR_DETAIL_MAX_PAGES and src/github/app.ts's workflow-run listing / MAX_WORKFLOW_RUN_LIST_PAGES, both bounded to 10) so a pathological PR/commit can't turn one read into an unbounded fetch loop.

Implementation

• Refactored the module's bespoke githubJson into githubJsonWithLink (returns { payload, link }) with githubJson kept as a thin wrapper, so existing callers are unchanged — this file uses its own timeoutFetch helper rather than Octokit, so backfill.ts's Octokit-based githubPaginatedList isn't directly importable; a local walker mirroring its shape is the sanctioned option per the issue.
• Added findAcrossPages(firstPageUrl, init, selectItems, probe): probes each page's items as it arrives and returns the first match, stopping early once found, when the Link header stops advertising a next page, or at the 10-page bound.
• Fail-safe preserved exactly (the file header's "Every helper degrades to null/absent on failure — preview discovery must NEVER sink a review"): each function keeps its try/catch returning null/"absent", and a mid-pagination failure falls back to what earlier pages already yielded (each page is probed as it arrives, so a later-page failure never drops a successful first page — mirroring githubPaginatedList's own contract). Page 1 stays the bare per_page=100 request (the &page=N cursor is added only for page 2+), so the single-page path is byte-identical to before.

Tests

test/unit/preview-url.test.ts adds regression tests exercising the real functions against mocked multi-page fetch responses with realistic Link headers: bot comment / Workers-Builds check found on page 2; early-exit once found (no further pages fetched); the PREVIEW_LIST_MAX_PAGES bound against a pathological always-rel="next" mock (asserts exactly 10 fetches, no unbounded loop); mid-pagination fetch-failure degrading to null/"absent" without throwing; plus the user-less / link-less-comment and nameless-check-run edge branches. Every changed line and branch is covered (verified via --coverage), so codecov/patch holds.

Validation

• git diff --check
• npm run typecheck (root tsc --noEmit) green
• npm run test:coverage on the affected suite: 100% of changed lines + branches covered (codecov/patch); existing preview-url / visual-capture tests pass unmodified
• Scope is src/review/visual/preview-url.ts + its unit test only — no API/OpenAPI/MCP/UI/DB/wrangler surface, so no generated artifact needs regeneration

Safety

• No secrets, wallets, hotkeys/coldkeys, PATs, private keys, raw trust scores, private rankings, or maintainer evidence.
• The bot-login restriction (cloudflare-workers-and-pages[bot], unspoofable [bot] suffix) is unchanged — pagination doesn't widen which comments are trusted for a server-rendered *.workers.dev URL.
• Auth/CORS/session: N/A. API/OpenAPI/MCP: N/A. UI: N/A. No changelog edit; no site//CNAME/lovable changes.

Closes #7450

[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 91.35%. Comparing base (25decd9) to head (7b8beb3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7469      +/-   ##
==========================================
- Coverage   91.35%   91.35%   -0.01%     
==========================================
  Files         716      716              
  Lines       72990    73004      +14     
  Branches    21628    21629       +1     
==========================================
+ Hits        66678    66690      +12     
  Misses       5272     5272              
- Partials     1040     1042       +2     

Flag	Coverage Δ
shard-1	32.67% <100.00%> (-0.01%)	⬇️
shard-2	36.12% <3.33%> (+<0.01%)	⬆️
shard-3	34.52% <3.33%> (-0.01%)	⬇️
shard-4	42.86% <3.33%> (-0.03%)	⬇️
shard-5	36.96% <16.66%> (-0.01%)	⬇️
shard-6	33.47% <53.33%> (-0.08%)	⬇️

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

Files with missing lines	Coverage Δ
src/review/visual/preview-url.ts	72.51% <100.00%> (+10.98%)	⬆️

... and 2 files with indirect coverage changes

[loopover-orb]

Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-20 11:22:16 UTC}

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

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This PR fixes a genuine truncation bug: findPreviewUrlFromPrComments and getPreviewBuildState each read only one per_page=100 page and would silently miss the bot's comment/check-run on a PR with >100 comments or a commit with >100 check-runs. The fix walks the Link: rel=next header via a new findAcrossPages helper bounded to 10 pages, mirroring the repo's existing pagination precedents in backfill.ts and app.ts, and preserves the fail-safe null/absent degrade-on-error contract. The change is well-scoped, the page-1 URL stays byte-identical to the pre-pagination request, and the test suite covers early-exit, non-array payloads, mid-pagination failure, and the page-bound cap.

Nits — 5 non-blocking

• src/review/visual/preview-url.ts:80 hasNextPage uses a naive `/rel="next"/` regex split on commas — a Link header value containing a comma inside a URL (unlikely but technically legal) could misparse; acceptable given GitHub's actual format but worth a one-line comment on the assumption.
• The 404 in getLatestDeploymentStatus (src/review/visual/preview-url.ts:~140) is unrelated pre-existing code, not part of this diff's magic-number surface — the external brief's flag on line 45 doesn't correspond to a new literal introduced by this change.
• test/unit/preview-url.test.ts's NEXT_LINK constant hardcodes `page=99` for both rel="next" and rel="last", which is harmless for these tests but slightly confusing since findAcrossPages ignores the URL in the Link header and always appends its own `&page=N`.
• Consider extracting the `/rel="next"/` regex in hasNextPage (preview-url.ts:80) into a named constant/comment noting it assumes GitHub's exact Link header format.
• The PR description states this closes fix(review): paginate preview-url.ts's PR-comment and check-run GitHub reads #7450 — confirm that issue is the correct eligible link since the external brief marks issue coverage as 'partial'.

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	#7450
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: 53 registered-repo PR(s), 29 merged, 0 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	xfodev; Gittensor profile; 53 PR(s), 0 issue(s).
Improvement	✅ Minor	risk: clean · value: minor · LLM: moderate

Linked issue satisfaction

Addressed
The diff adds a bounded, Link-header-driven pagination helper (findAcrossPages, PREVIEW_LIST_MAX_PAGES=10) and applies it to both findPreviewUrlFromPrComments and getPreviewBuildState, preserving the null/absent fail-safe contract including mid-pagination failures. It includes regression tests for multi-page discovery, early-exit on found match, mid-page fetch failure fallback, and the max-page bo

Review context

• Author: xfodev
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: JavaScript, TypeScript
• Official Gittensor activity: 53 PR(s), 0 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.