feat: retry transient 5xx errors in withSpinner

[bukinoshita]

Summary

Resolves BU-639: Template automation exits on transient Resend 5xx failures.

The withSpinner() retry wrapper previously only retried rate_limit_exceeded (HTTP 429) errors. Transient server-side 5xx responses (internal_server_error, service_unavailable, gateway_timeout) caused immediate command failure — problematic for CI jobs and agent-driven template management.

Changes

• src/lib/is-transient-error.ts — New utility predicate that identifies transient 5xx-class error names from the Resend SDK.
• src/lib/spinner.ts — Changed withSpinner first parameter from a plain string to a SpinnerMessages object with an optional retryTransient flag. When enabled, transient errors are retried with the same exponential backoff policy as rate limits.
• src/lib/actions.ts — Enabled retryTransient by default for safe read operations (runGet, runList). Added opt-in retryTransient field to runWrite config. Left runCreate and runDelete without transient retries to avoid duplicate side effects on non-idempotent operations.
• src/commands/templates/update.ts and src/commands/templates/publish.ts — Opted into transient retries since these are idempotent write operations.
• Direct withSpinner callers (emails/send.ts, emails/batch.ts, emails/receiving/attachment.ts, contacts/update-topics.ts) — Updated to use the new object signature. Attachment fetch gets retryTransient: true (read-only); send/batch/update-topics do not (non-idempotent).

Testing

• Added tests/lib/is-transient-error.test.ts with 6 tests covering all transient names plus negative cases.
• Added withSpinner retry on transient 5xx errors describe block in tests/lib/spinner.test.ts with 6 tests:
  • Retries each transient error name when retryTransient: true
  • Does not retry transient errors when retryTransient is not set
  • Exhausts max retries and errors on persistent transient failures
  • Still retries rate_limit_exceeded regardless of retryTransient flag
• All 747 tests pass, lint and typecheck clean.

Linear Issue: BU-639

  

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Summary by cubic

Add opt-in retries for transient 5xx errors in withSpinner to make read paths and idempotent template writes resilient to brief outages. Addresses BU-639 by preventing failures on internal_server_error, service_unavailable, and gateway_timeout.

• New Features

  • withSpinner now accepts { loading, retryTransient? }; always retries rate_limit_exceeded, and when retryTransient is true, also retries transient 5xx with the same backoff/retry-after logic.
  • Default retryTransient: true for runGet and runList; optional on runWrite (enabled for templates:update and templates:publish; left off for create, delete, emails:send, emails:batch; enabled for read-only emails:receiving:attachment).
  • Added isTransientError utility.

• Migration

  • Replace withSpinner('message', ...) with withSpinner({ loading: 'message' }, ...).
  • For idempotent or read-only operations, set retryTransient: true; keep it off for non-idempotent writes.
  • No changes needed where runGet/runList are used (they now retry transient errors by default).

^{Written for commit 1628223. Summary will update on new commits.}