Replace the LLMError { module, method, reason } wrapper with a flat
tagged union (LLM.BadRequest, LLM.Authentication, LLM.PermissionDenied,
LLM.NotFound, LLM.RateLimit, LLM.QuotaExceeded, LLM.ContentPolicy,
LLM.ContextOverflow, LLM.ServerError, LLM.APIError, LLM.ConnectionError,
LLM.TimeoutError, LLM.MalformedResponse, LLM.NoRoute) plus an isLLMError
guard. Add one shared classifyApiFailure classifier used by the HTTP
executor and the AI SDK adapter so both surfaces classify identically,
preserving status, headers, body, and retry-after.
Core policy moves onto tags: retry RateLimit | ServerError |
ConnectionError | TimeoutError; toSessionError adds
provider.context-overflow, provider.timeout, and provider.not-found.
The provider-error stream event and the runner's held-back overflow
handling are unchanged here; isContextOverflowFailure now bridges old
events and new tags until the event is removed.
