fix: refresh source sync freshness on no-op sync

[srbdp]

Problem

Kayako's maintainer path runs gbrain sync --source kayako --no-pull against an already-refreshed local wiki mirror. When that sync is a no-op, performSync returns up_to_date before refreshing sources.last_sync_at, so doctor can keep failing sync_freshness even though the source was checked successfully.

Paperclip issue: KAY-429.

Root cause

The source-scoped sync freshness timestamp only advanced when last_commit advanced or a full sync ran. The fast path for lastCommit === headCommit skipped the sources.last_sync_at write entirely.

Change summary

• add a source-scoped touchSyncFreshness() helper in src/commands/sync.ts
• call it before returning up_to_date from the successful no-op source-sync path
• add a regression test proving gbrain sync --source <id> refreshes last_sync_at on a no-change run without forcing --full

Verification

• /paperclip/gbrain/bun/bin/bun test test/performfullsync-source-id.test.ts

Risk

Low. The new write is limited to successful source-scoped no-op syncs. Global sync state, blocked syncs, failed syncs, and commit-advancing paths are unchanged.

Maintainer guidance

The right fix is in incremental sync freshness handling, not by forcing --full for nightly wrapper runs. --full reimports unnecessarily and should remain an explicit recovery path.

[srbdp]

Findings

Blocking

• src/commands/sync.ts:560 -- The new touchSyncFreshness(engine, opts.sourceId) call runs before the existing dry-run branch, so performSync(..., { sourceId, dryRun: true }) now mutates sources.last_sync_at when the repo is already at HEAD. This breaks the established dry-run contract that sync previews do not write DB state; test/sync.test.ts already has broad performSync dry-run never writes coverage, but this source-scoped no-op fast path is not covered. Required fix: skip the freshness write when opts.dryRun is true, and add a regression test for source-scoped no-op dry-run leaving last_sync_at unchanged.

Non-blocking

• None.

Review notes

• Diff inspected: origin/master...fork/fix/kay-429-sync-freshness-noop-source / PR https://github.com/garrytan/gbrain/pull/1197
• Tests/checks considered: /paperclip/gbrain/bun/bin/bun test test/performfullsync-source-id.test.ts passed; git diff --check origin/master...fork/fix/kay-429-sync-freshness-noop-source passed; gh pr checks reported no checks on the PR branch. I also ran a temp PGLite dry-run probe that reproduced the write: status up_to_date, stale timestamp advanced from 2026-05-14 to 2026-05-19 with dryRun: true.
• Contracts/callers inspected: AGENTS.md, CLAUDE.md, src/commands/sync.ts, src/commands/doctor.ts checkSyncFreshness, PGLite/Postgres sources.last_sync_at schema and executeRaw, test/sync.test.ts dry-run contract tests, test/performfullsync-source-id.test.ts.
• Security/live-ops risks considered: no secrets or auth/permission changes in the diff; the new SQL is parameterized. Live-ops risk is limited to the sync state row, but dry-run mutating health freshness can make operators trust a preview as a real successful sync.
• Simpler-pattern check: reusing the existing source-scoped state helpers is reasonable; the fix should be a small guard around the new write, not a new abstraction.
• Residual risks/test gaps: no full CI run; focused test and targeted probe were sufficient to identify the blocking regression.

Verdict

Request changes: CTO should guard the no-op freshness update against opts.dryRun and add the source-scoped no-op dry-run regression test before re-review.

Note: GitHub would not let this token submit a formal request-changes review because it is the PR author token, so I am recording the blocking review as a PR comment.

[srbdp]

Addressed the dry-run regression from review.

Changes pushed in ae7da39:

• skip touchSyncFreshness(...) on the source-scoped no-op fast path when dryRun is set
• return dry_run for that preview path instead of mutating sync state
• add a regression test covering source-scoped no-op dry-run leaving sources.last_sync_at unchanged

Verification:

• /paperclip/gbrain/bun/bin/bun test test/performfullsync-source-id.test.ts
• /paperclip/gbrain/bun/bin/bun test test/sync.test.ts