Consolidate command execution output into aggregated_output (#50402)

## What changed

- Remove `stdout`, `stderr`, and `formatted_output` from `CommandExecutionItem` and `ExecCommandEndEvent`, retaining `aggregated_output` as the output field.
- Update command event producers, legacy conversion, rollout traces, and the precomputed schema. Use aggregated output for terminal trace results.
- Clear `interaction_input` in emitted and migrated command completion items.

## Testing

Update command execution and trace tests to use aggregated output, and assert that legacy rollout migration preserves `aggregatedOutput`.

GitOrigin-RevId: ed59827d4a5ec9a767084ee4feac72c2042440f2

codex-rs/app-server-protocol/src/protocol/v2/tests.rs

@@ -3330,12 +3330,9 @@ fn core_turn_item_into_thread_item_converts_supported_variants() {
         source: CoreExecCommandSource::Agent,
         interaction_input: None,
         status: CoreCommandExecutionStatus::Completed,
-        stdout: Some("done\n".to_string()),
-        stderr: Some(String::new()),
         aggregated_output: Some("done\n".to_string()),
         exit_code: Some(0),
         duration: Some(Duration::from_millis(5)),
-        formatted_output: Some("done\n".to_string()),
     });
 
     assert_eq!(