Stop retrying explicit invalid-workspace errors (#60475)

## Why

HTTP 403 responses with `invalid_workspace_selected` were treated as unexpected status errors, allowing retries and compaction fallback to another model after the server rejected the selected workspace.

## What changed

Recognize the code in `detail.code` or `error.code`, falling back to the `x-error-json` header when the body has no code. Classify these 403 responses as `InvalidWorkspaceSelected` and disable retries and compaction model fallback while preserving the response details and HTTP status. Other 403 responses retain their existing retry behavior.

## Testing

Add coverage for body and header error codes, code precedence, HTTP and WebSocket retry behavior, and local and remote compaction during a model downshift.

GitOrigin-RevId: f44a3bee5ef06e601909839868ab99cea6dd7d03

codex-rs/core/src/compact_model_fallback.rs

@@ -17,6 +17,7 @@ pub(crate) fn should_retry_with_current_model(
         CodexErrorDetails::TurnAborted
             | CodexErrorDetails::Interrupted
             | CodexErrorDetails::SessionBudgetExceeded
+            | CodexErrorDetails::InvalidWorkspaceSelected(_)
             | CodexErrorDetails::ResponseIncomplete(_)
     ) || (previous.model_info().slug == current.model_info().slug
         && previous.cyber_access_program == current.cyber_access_program)