* feat(mail): return typed error envelopes across the mail domain
Replace every produced error path in shortcuts/mail with typed errs.* envelopes, so consumers get stable category, subtype, param/params, hint, retryable, and log_id metadata for classification and recovery instead of free-form message text.
- Locally constructed mail errors move from output.Err* / output.Errorf / final fmt.Errorf / common legacy helpers to errs.* builders, with structured params on multi-flag validation and failed-precondition states kept non-retryable.
- API-call failures move from runtime.CallAPI / DoAPIJSON legacy boundaries to runtime.CallAPITyped or runtime.ClassifyAPIResponse, and mail-specific enrichers read errs.ProblemOf so typed code, subtype, hint, and log_id metadata are preserved.
- Batch draft-send partial failures now use runtime.OutPartialFailure so successful and failed draft sends stay in stdout while the command exits through a typed multi-status signal.
- Add mail-domain typed helpers, mail API code metadata, and guard wiring to keep shortcuts/mail from reintroducing legacy envelopes or legacy API calls.
- Keep genuine intermediate fmt.Errorf wraps in parser/builder layers annotated with nolint comments; command-facing paths wrap them into typed validation, API, network, or internal errors.
* fix(mail): report aborted draft-send batches as a single failure result
When an account-level failure interrupts a batch send after some drafts
already went out, the command previously produced two machine-readable
failure results: the partial-failure ledger on stdout and a second error
envelope on stderr. Consumers could not tell which one to recover from.
The batch ledger is now the only failure result for that case: it gains
aborted and abort_error fields carrying the typed cause, so callers can
see which drafts were sent, which failed, why the batch stopped, and how
to recover — all from stdout. A --stop-on-error stop keeps these fields
unset because stopping early there is the caller's own choice.
