fix(core,web): retry transport and quota LLM errors, disable dead sessions on auth failure (#82)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/docs/content/architecture.en.md

@@ -129,7 +129,7 @@ The Server keeps an additional SQLite index (users, authorization, usage stats)
 ## Key design decisions
 
 - **One protocol, three jobs**: OmniMessage is simultaneously the SDK's external interface, the Trace on-disk format and the engine's internal currency — what streams, what is stored and what the model sees are the same thing.
-- **Errors converge into messages**: the LLM and Environment never throw into the engine; results carry a five-value `stop_reason` (`completed | failed | aborted | timeout | malformed`), and only LLM-side `timeout / malformed` trigger an in-run reconnect.
+- **Errors converge into messages**: the LLM and Environment never throw into the engine; results carry a six-value `stop_reason` (`completed | failed | aborted | timeout | malformed | auth`), and only LLM-side `timeout / malformed` trigger an in-run reconnect (up to 5 times with an exponential-with-ceiling backoff — `timeout` covers network timeouts, transport disconnects and transient provider quota errors; `auth` stops like `failed`).
 - **A thin model layer**: core defines only `LLMInterface`; provider adaptation lives entirely in AgentHub (`@prismshadow/agenthub`), which is what makes any OpenAI-compatible endpoint reachable. See [Models & Providers](/models).
 
 Source entry points: `packages/core/src/engine/context-engine.ts`, `packages/core/src/interfaces.ts`.