Separate thread settings from environment configuration (#39597)

## Why

Environment-owned permission profiles and workspace roots must remain effective
without being persisted or restored as thread-owned settings.

## What changed

- Keep thread settings snapshots and restore data separate from the effective
  configuration supplied by the primary environment.
- Use resolved environment permissions, active profiles, workspace roots, and
  network policy when building turn context and session events.
- Preserve environment selections when agents are evicted, resumed, or spawned,
  and validate owner configuration when it becomes ready.
- Start memory initialization only after the primary environment is configured.

## Testing

- Extend remote-environment and multi-agent tests to cover settings persistence,
  owner permission profiles, workspace roots, spawning, eviction, and resume.

GitOrigin-RevId: d82f126981cd0190233020bbdd61d96c70558868

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

@@ -139,6 +139,12 @@ impl Session {
         };
 
         environment.config = config;
+        if matches!(environment.config, EnvironmentConfigState::Ready(_)) {
+            state
+                .session_configuration
+                .validate(&environments)
+                .map_err(|error| CodexErr::InvalidRequest(error.to_string()))?;
+        }
 
         // Invalidate MCP before installed configuration can wake a waiting turn.
         self.mark_mcp_runtime_dirty();