fix(db): add $defaultFn(nowIso) to upstreamDriftReports.updatedAt

[claytonlin1110]

What

upstreamDriftReports.updatedAt was the only updatedAt in src/db/schema.ts missing .$defaultFn(() => nowIso()), despite the file header's house rule (and ~30 sibling columns that already follow it). Current writers always pass updatedAt explicitly, so nothing breaks today — but any future insert that omits the column would hit the same client-side corruption class the header documents.

Changes

• Added .$defaultFn(() => nowIso()) to upstreamDriftReports.updatedAt only — generatedAt and repository writers left untouched.
• Regression in test/unit/schema-timestamp-defaults.test.ts: drizzle insert that omits updatedAt gets a real ISO-8601 timestamp (not CURRENT_TIMESTAMP / empty).

Closes

Closes #8369

Verification

• npx vitest run test/unit/schema-timestamp-defaults.test.ts — 7 passed (including the new omit-path case)

[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 89.45%. Comparing base (af270b9) to head (4f7031c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8404      +/-   ##
==========================================
- Coverage   92.42%   89.45%   -2.97%     
==========================================
  Files         791       98     -693     
  Lines       79250    22892   -56358     
  Branches    23946     3872   -20074     
==========================================
- Hits        73243    20477   -52766     
+ Misses       4868     2237    -2631     
+ Partials     1139      178     -961     

Flag	Coverage Δ
shard-1	66.12% <0.00%> (+9.76%)	⬆️
shard-2	66.66% <0.00%> (+13.58%)	⬆️
shard-3	70.43% <100.00%> (+17.38%)	⬆️

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

Files with missing lines	Coverage Δ
src/db/schema.ts	73.11% <100.00%> (+0.14%)	⬆️

... and 693 files with indirect coverage changes

[loopover-orb]

Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-24 12:04:52 UTC}

2 files · 1 AI reviewer · no blockers · readiness 93/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
Small, correct schema fix: adds `.$defaultFn(() => nowIso())` to `upstreamDriftReports.updatedAt`, matching the house rule already applied to ~30 sibling timestamp columns in this file, and closes the last gap referenced by issue #8369. The accompanying test correctly inserts via drizzle omitting `updatedAt` and asserts a real ISO-8601 value (not `CURRENT_TIMESTAMP` or empty), which is the right regression shape for this class of bug. No migration is needed since this changes only client-side insert behavior, not the column's type/nullability/default at the SQL level.

Nits — 3 non-blocking

• No migration file is added, which is correct here since `$defaultFn` is a drizzle-side JS default (no SQL schema change) — worth a one-line note in the PR description for future reviewers who reflexively look for a migration on any `schema.ts` diff.
• The upstreamDriftReports repository writer (`upsertUpstreamDriftReport` per test/unit/db-persistence.test.ts) still always passes `updatedAt` explicitly, so this defaultFn is currently dead code on all real write paths — fine per the PR's own framing as forward-looking hardening, but worth confirming no other in-repo caller already relies on omission behaving differently.
• Consider a short follow-up sweep confirming `generatedAt`-style non-updatedAt timestamp columns across the file don't have similar gaps, since the PR explicitly scoped itself to only `updatedAt`.

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	#8369
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: 394 registered-repo PR(s), 251 merged, 92 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	claytonlin1110; Gittensor profile; 394 PR(s), 92 issue(s).
Improvement	✅ Minor	risk: clean · value: minor · LLM: minor

Linked issue satisfaction

Addressed
The diff adds `.$defaultFn(() => nowIso())` to `upstreamDriftReports.updatedAt` matching the sibling pattern, leaves `generatedAt` and the repository writers untouched, and includes a regression test that inserts a row omitting `updatedAt` and asserts a real ISO-8601 timestamp is produced.

Review context

• Author: claytonlin1110
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: Python, JavaScript, TypeScript, Rust
• Official Gittensor activity: 394 PR(s), 92 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Start here: Triage stale or unlinked PRs.

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.