fix(backfill): drop unparseable timestamps from the latestDate reduction

[RenzoMXD]

Summary

latestDate (src/github/backfill.ts) selects the contributor's latest activity timestamp with a lexicographic .sort().at(-1) and only a truthiness filter:

function latestDate(values: Array<string | null | undefined>): string | undefined {
  return values.filter(Boolean).sort().at(-1) ?? undefined;
}

A malformed/sentinel GitHub timestamp whose first character sorts after 2 (e.g. bad-date, pending, not-a-date) therefore wins over a real 2026-... ISO stamp and is persisted into contributor_repo_stats.last_activity_at. Every downstream freshness check then does Date.parse(bad-date) -> NaN and treats a genuinely active repo as stale/missing.

Fix

Mirror the guarded canonical form already in src/signals/data-quality.ts (newest()/oldest()):

return values?.filter((value): value is string => Boolean(value && Number.isFinite(Date.parse(value)))).sort().at(-1);

Also require Number.isFinite(Date.parse(value)) in latestDate's filter, so unparseable values are dropped from the reduction. No behavior change when every value is a well-formed ISO timestamp.

Regression proof

An existing test (test/unit/backfill.test.ts) feeds a fixture mixing updatedAt: bad-date with valid ISO stamps and previously asserted lastActivityAt: bad-date -- encoding the bug. That assertion is corrected to the real latest stamp (2026-05-24T00:00:00Z); the flip is the regression proof (pre-fix the malformed value won the lexicographic max; post-fix it is dropped).

Scope

• The PR title follows type(scope): short summary Conventional Commit format.
• 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 an issue (fix(backfill): a malformed GitHub updatedAt must not outrank a real timestamp in lastActivityAt #1714).

Validation

• git diff --check
• npm run actionlint
• npm run db:migrations:check
• npm run typecheck
• npm run test:coverage -- test/unit/backfill.test.ts 94/94 pass; the changed filter is covered (both arms: the malformed bad-date is dropped, the valid ISO stamps are kept).

Targeted run:

npx vitest run test/unit/backfill.test.ts
# 94/94 passed

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• No auth, cookie, CORS, GitHub App, Cloudflare, or session changes -- a pure-helper timestamp reduction on the contributor-activity ingestion path, using a guard pattern already established in the same codebase.
• No UI changes.
• No docs/changelog changes.

UI Evidence

Not applicable -- backend timestamp-reduction helper with no visible UI, frontend, docs, or extension surface.

Closes #1714

[gittensory-orb]

Warning

🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨

⏸️ Gittensory review result - manual review recommended

_{Review updated: 2026-06-29 14:12:43 UTC}

2 files · 1 AI reviewer · no blockers · readiness 55/100 · CI green · clean

⏸️ Suggested Action - Manual Review

• Touches a guarded path — held for manual review

Review summary
This changes the backfill `latestDate` helper to ignore truthy but unparseable activity timestamps before selecting the lexicographic maximum. For GitHub ISO `updatedAt` values, the ordering remains correct while malformed values like `bad-date` no longer win and get stored as `lastActivityAt`; the updated test drives the real `refreshContributorActivity` path. I do not see a reachable correctness defect in this diff.

Nits — 8 non-blocking

• src/github/backfill.ts:2809: nit: The inline predicate is long enough to obscure the actual reduction; a small named helper would match the existing `newest()` pattern and make the guard reusable.
• test/unit/backfill.test.ts:287: nit: The mixed-validity regression is covered, but there is no explicit all-invalid case documenting that `latestDate` should return `undefined` rather than preserving any malformed timestamp.
• src/github/backfill.ts:2809: Extract the parseability check into a local `isParseableDateString` helper or share the same helper shape used by `src/signals/data-quality.ts:newest`.
• test/unit/backfill.test.ts:287: Add a focused assertion where every candidate timestamp is invalid so the no-valid-date behavior is locked down.
• 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.
• Code changes lack test evidence — Add focused regression tests or explain why existing coverage is sufficient.
• Readiness score is below the configured threshold — Use the readiness panel as advisory maintainer context; the score does not block this PR.
• Touches a guarded path — held for manual review — A maintainer must review and merge this change.

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	✅ Linked	#1714
Related work	⚠️ 2 scoped overlaps	Top overlaps are listed below; lower-confidence bulk is hidden.
Review load	❌ 8/20	Readiness component derived from cached public PR metadata and labels.
Validation evidence	❌ 5/25	Cached preflight status is hold.
Open PR queue	❌ 3/10	22 open PR(s), 10 likely reviewable, 12 unlinked.
Contributor context	✅ Confirmed Gittensor contributor	RenzoMXD; Gittensor profile; 44 PR(s), 9 issue(s).
Gate result	⚠️ Not blocking	Advisory; not blocking this PR.

Review context

• Author: RenzoMXD
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository registration is not available in the local Gittensory cache.
• Public profile languages: not available
• Official Gittensor activity: 44 PR(s), 9 issue(s).
• Related work: Items reference the same linked issue fix(backfill): a malformed GitHub updatedAt must not outrank a real timestamp in lastActivityAt #1714. (issue #1714)
• Related work: Open PR work references issue fix(backfill): a malformed GitHub updatedAt must not outrank a real timestamp in lastActivityAt #1714. (issue #1714)

Contributor next steps

• Review top overlaps.
• Add scope summary.
• Fix blocker.
• Expect slower review.
• Refresh registry data or choose a registered active repo.
• Check active issues and PRs before submitting.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Review load = cached public PR metadata such as size labels, changed paths, and preflight status.
• Open PR queue = repo-wide review pressure; it is not a PR 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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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.58%. Comparing base (59cf13f) to head (a9e26be).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1715   +/-   ##
=======================================
  Coverage   95.58%   95.58%           
=======================================
  Files         204      204           
  Lines       22313    22313           
  Branches     8065     8064    -1     
=======================================
  Hits        21328    21328           
  Misses        408      408           
  Partials      577      577           

Files with missing lines	Coverage Δ
src/github/backfill.ts	92.95% <100.00%> (ø)

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