feat(backfill): reuse GitHub totals snapshots

[oktofeesh1]

Summary

• Reuse fresh GitHub totals snapshots across open-data backfill enqueue and segment jobs.
• Fall back only to valid same-source snapshots and coalesce concurrent totals refreshes.
• Closes Reduce duplicate GitHub totals queries during open-data backfill #1855

What changed

• Added a bounded totals snapshot selector that skips future-dated, malformed, and source-mismatched rows.
• Shared the selector between enqueue, segment workers, and sync-state rollup fallback counts.
• Added in-process single-flight for live totals refreshes by repository/source.
• Covered fresh reuse, stale refresh/fallback, invalid snapshot rejection, no-token fallback, older-valid history fallback, and concurrent coalescing.

Why

• Reduces repeated GitHub GraphQL totals queries during scheduled and manual self-hosted open-data backfill bursts while keeping expected-count decisions conservative.

Validation

• npx vitest run test/unit/backfill.test.ts
• npm run test:ci
• npm audit --audit-level=moderate

[gittensory-orb]

Warning

🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨

⏸️ Gittensory review result - manual review recommended

_{Review updated: 2026-06-30 19:05:41 UTC}

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

⏸️ Suggested Action - Manual Review

• Touches a guarded path — held for manual review

Review summary
The change centralizes totals snapshot selection for backfill enqueue, segment work, and sync-state rollup, and it adds a per-process single-flight around live totals refreshes. The visible logic correctly rejects source-mismatched, future-dated, and malformed rows before falling back, and the tests cover the main reuse/refresh/fallback paths. The main review risk is ordering: the selector’s correctness depends on `listRepoGithubTotalsSnapshotHistory` returning rows oldest-to-newest, but that contract is not visible in this diff.

Nits — 7 non-blocking

• nit: `src/github/backfill.ts:498` relies on the snapshot-history ordering when scanning from `snapshots.length - 1`; add an inline comment or make `listRepoGithubTotalsSnapshotHistory` return/order contract explicit so a future repository helper change does not silently make this choose the oldest valid snapshot.
• nit: `test/unit/backfill.test.ts:1439` does not distinguish ascending from descending history because the latest row is invalid; add a case with two valid same-source snapshots and assert the newer one wins.
• In `test/unit/backfill.test.ts`, add a valid-newer-versus-valid-older snapshot test for `backfillRepositorySegment` or enqueue so the selector’s “latest valid” behavior is locked down.
• In `src/github/backfill.ts`, consider changing the selector loop to operate on a helper with an explicit name such as `latestUsableRepoGithubTotalsSnapshot` if the repository API is intentionally ordered oldest-to-newest.
• 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.
• 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	#1855
Related work	⚠️ 3 scoped overlaps	Top overlaps are listed below; lower-confidence bulk is hidden.
Change scope	❌ 8/20	High review scope from cached public metadata (size label size:M; 1 linked issue).
Validation posture	❌ 5/25	Preflight is holding this PR; address the blocker before review.
Contributor workload	✅ 10/10	Author activity: 71 registered-repo PR(s), 60 merged, 7 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	oktofeesh1; Gittensor profile; 71 PR(s), 7 issue(s).
Gate result	⚠️ Not blocking	Advisory; not blocking this PR.

Review context

• Author: oktofeesh1
• 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: 71 PR(s), 7 issue(s).
• Related work: Items reference the same linked issue Reduce duplicate GitHub totals queries during open-data backfill #1855. (issue #1855)
• Related work: Open PR work references issue Reduce duplicate GitHub totals queries during open-data backfill #1855. (issue #1855)
• Related work: Items reference the same linked issue feat(enrichment): Churn-hotspot + bug-density scorer #1513. (issue #1513, PR #1882)
• Additional title-only matches omitted; title-only overlap does not block.

Contributor next steps

• Review top overlaps.
• Add a concise scope and risk note.
• Fix the blocker.
• Triage stale or unlinked PRs.
• 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.
• 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.

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

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