## Why
Model requests need the selected workspace's routing constraints before sending content. A missing cached route cannot establish that a custom ChatGPT-auth destination is independent of the workspace.
## What changed
- Register the account processor as the workspace routing resolver for Responses HTTP, compaction, and WebSockets, enabling origin selection and routing headers while preserving API paths and rejecting routed HTTP redirects.
- Share concurrent discovery by auth generation, workspace, and backend configuration. Recover from discovery-time `401` responses while allowing token refreshes for the same auth owner.
- Require successful discovery before classifying custom destinations as independent, and require a new thread when a workspace-bound session's bootstrap origin changes.
- Refresh managed requirements using retained session configuration without fetching thread configuration again. Return typed routing errors without account or backend details.
## Testing
Extend coverage for discovery-time token refresh, retained provider definitions under managed requirements, and specific invalid-routing error categories.
GitOrigin-RevId: 090cda70daa91ee8acfbc973699d028111e54125
0a5b999169