Error Handling & Observability

Core principles (non-negotiable)

1. Fail fast and loudly — surface errors where they occur, don't bury them three layers deep.
2. Typed errors over string messages — errors are structured values, not just message strings to pattern-match against.
3. User messages ≠ developer messages — friendly text to the user, full context (stack, request details) in logs only. Never expose internals externally (ties to warisskill-security-practices).
4. Never swallow errors silently — every catch either handles, re-throws, or logs. An empty catch block is always wrong.
5. Errors are part of the API contract — every error code a client can receive gets documented, same envelope shape as warisskill-system-design-api-design.

Style: throw/catch as default, Result pattern for expected failures