test(enrichment): cover churn-hotspot empty-list and threshold boundaries

[dhgoal]

Summary

Hardens unit coverage for the churn-hotspot analyzer's pure helpers with two edge cases the existing threshold test doesn't exercise:

• summarizeChurn([]) — an empty commit list must be zero churn (fixFraction: 0), exercising the commitCount ? fixCount / commitCount : 0 divide-by-zero guard's else branch (the existing test only feeds 10 commits).
• isHotspot at the exact >= thresholds — {commitCount: 8, fixFraction: 0.3} is inclusive (a hotspot), while one step below either floor (7 commits, or 0.29 fix-fraction) is not. The existing test only checks values well above/below, not the boundary.

Test-only, against the compiled dist/, in the analyzer's own test file. No source or shared-registry change; the pure helpers are already imported by this file, so no new import surface.

No linked issue — straightforward boundary/edge coverage hardening of pure functions; changes no runtime behavior.

Scope

• Conventional Commit; focused; touches only review-enrichment/test/churn-hotspot.test.ts. No site//CNAME/**/lovable/**; no CHANGELOG.md.

Validation

• npm --prefix review-enrichment test — 966 pass / 0 fail (build + sourcemap validate + metadata --check + node tests; exactly CI).
• git diff --check clean.

Safety

• Test-only, no runtime change. No secrets/wallets/hotkeys/trust/reward terms.

[superagent-security]

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

[loopover-orb]

Warning

🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨

⏸️ Gittensory review result - manual review recommended

_{Review updated: 2026-07-05 05:54:24 UTC}

1 file · 1 AI reviewer · no blockers · readiness 80/100 · CI green · clean

⏸️ Suggested Action - Manual Review

Review summary
This is a focused test-only change that adds real coverage for the empty-list churn summary path and the exact inclusive hotspot thresholds. The new assertions exercise the pure helpers already imported by this test file, and the cases line up with the described `commitCount ? ... : 0` guard and `>=` behavior. I do not see a reachable correctness issue in the diff.

Nits — 2 non-blocking

• nit: review-enrichment/test/churn-hotspot.test.ts:39 and review-enrichment/test/churn-hotspot.test.ts:44 duplicate implementation details in comments, so they will become stale if the helper thresholds or guard expression are refactored without changing behavior.
• review-enrichment/test/churn-hotspot.test.ts:44: Keep the boundary test, but consider making the test body the source of truth and trimming the comment to avoid restating the exact operators already enforced by the assertions.

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	✅ No-issue rationale	PR body explains why no issue is linked.
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 (no linked issue context).
Validation posture	❌ 5/25	Preflight is holding this PR: the review lane is unavailable, so it is not ready for automated review.
Contributor workload	✅ 10/10	Author activity: 69 registered-repo PR(s), 42 merged, 0 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	dhgoal; Gittensor profile; 69 PR(s), 0 issue(s).
Gate result	✅ Passing	No configured blocker found.

Review context

• Author: dhgoal
• 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: 69 PR(s), 0 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Await review-lane availability.
• Refresh registry data or choose a registered active repo.
• Link the issue being solved, or explicitly explain why this is a no-issue PR.

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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[loopover-orb]

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