Frontend + Desktop: No Silent Catch

Frontend and desktop runtime code must not silently swallow exceptions.

Rationale:
- Silent catches hide failures, break observability, and make recovery behavior unpredictable.

Scope:
- PR review policy for runtime code under:
  - `domains/frontend/mem-client/src/**`
  - `domains/typescript/mem-client-desktop/src/**`
  - `domains/typescript/mem-client-desktop/preload/**`
- Excludes tests and stories.

Trigger:
- A PR adds or changes `catch` blocks in scope.

Approval checks:
1) New/changed catch blocks are not empty and do not use pass-only suppression.
2) Each new/changed catch block performs at least one explicit handling action:
   - rethrow,
   - structured logger call,
   - explicit fallback return/path.
3) Catch blocks that intentionally continue execution include an explicit fallback/control-flow path (not silent swallow-and-continue).

Evidence:
- Diff shows handling actions in each changed catch path.

Exception path:
- Allow deviation only when all are true:
1) PR description includes `Policy Exception: frontend-desktop-no-silent-catch`.
2) PR explains why suppressing the error is safe for this path.
3) PR documents compensating signal (for example metrics/logging/guard rails) and fallback behavior.

Decision:
- Return NOT APPROVED when trigger is met and exceptions are silently suppressed without a valid exception.