Recover capability discovery after executor disconnects (#38420)

## Why

Transient executor disconnects could leave capability discovery and skill catalogs
stuck on a cached failure for the rest of a thread, even after the executor
reconnected.

## What changed

- Replay capability discovery after executor recovery and retry transient failures
  on later requests while continuing to cache permanent failures.
- Avoid caching skill catalogs produced from failed discovery so a later step can
  load the recovered catalog.
- Mark the MCP runtime dirty when recovered manifests change the projected MCP
  servers, and allow discovery to be cancelled with the turn.

## Testing

- Cover same-request recovery after a disconnect and recovery on a later request.
- Cover retry classification through connection-attempt errors and skill catalog
  caching after discovery recovers.

GitOrigin-RevId: a57f90844351e73ea831931f72a9ddc4e4f3335c

codex-rs/core/src/session/mod.rs

@@ -3143,7 +3143,8 @@ impl Session {
                 &environments,
                 turn_context.windows_sandbox_level,
             )
-            .await;
+            .or_cancel(cancellation_token)
+            .await?;
         let extension_data = codex_extension_api::ExtensionData::new(turn_context.sub_id.clone());
         extension_data.insert(selected_capability_roots.clone());
         if let Some(discovery) = &executor_capability_discovery {