feat: guard git enrichment (#26175)

Skip turn git metadata enrichment when a turn has remote or multiple
executors, so we do not report the orchestrator checkout as executor
workspace metadata.

Test: `just test -p codex-core` (blocked by existing
`Session::conversation_id` compile error in `close_agent.rs`).

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

@@ -814,7 +814,13 @@ impl Session {
             turn_context.final_output_json_schema = final_schema;
         }
         let turn_context = Arc::new(turn_context);
-        turn_context.turn_metadata_state.spawn_git_enrichment_task();
+        if turn_context
+            .environments
+            .single_local_environment_cwd()
+            .is_some()
+        {
+            turn_context.turn_metadata_state.spawn_git_enrichment_task();
+        }
         turn_context
     }