docs: note external db sync timeout mitigation

Author: BilalG1

claude/CLAUDE-KNOWLEDGE.md

@@ -8,3 +8,6 @@ A: Use the shared `TextAreaField` component's `helperText` prop in `apps/dashboa
 
 Q: Why did `pnpm typecheck` fail after deleting a Next.js route?
 A: The generated `.next/types/validator.ts` can keep stale imports for removed routes. Deleting that file (or regenerating Next build output) clears the outdated references so `pnpm typecheck` succeeds again.
+
+Q: Why can external DB sync tests time out in dev-focused GitHub workflows?
+A: The first calls to `/api/latest/internal/external-db-sync/sequencer` and `/poller` can be slow in dev mode and hit Undici's headers timeout; prewarming those endpoints with the cron secret, retrying header-timeout failures in the test helper, or running tests single-worker are viable mitigations.