- extractErrorMessage(err: unknown) normalizes any error shape to string
- handleError/handleInfraError dual utilities (user-facing vs infra-only)
- error-classifier extended with ipc/database/filesystem types (9 total)
- Toast rate-limiting (max 3 per type per 30s) in notifications store
- Infrastructure bridges use documented console.warn (recursion prevention)
- 13 new tests for extractErrorMessage