test: clean up apply_patch allow-session artifact (#24611)

## Why

The
`approving_apply_patch_for_session_skips_future_prompts_for_same_file`
integration test writes `apply_patch_allow_session.txt` under the
process cwd while exercising outside-workspace patch approval behavior.
With `just test` now being the normal validation path, that file can be
left behind in the checkout when the test runs or fails, creating
confusing untracked state.

## What changed

- Registers the resolved `apply_patch_allow_session.txt` path with
`tempfile::TempPath` before the test removes and recreates it through
`apply_patch`.
- Preserves the existing outside-workspace path shape so the approval
behavior under test does not change.
- Lets `TempPath` remove the generated file when the test exits,
including panic paths.

## Verification

- `just test -p codex-core --test all
approving_apply_patch_for_session_skips_future_prompts_for_same_file`

codex-rs/core/tests/suite/approvals.rs

@@ -2073,6 +2073,7 @@ async fn approving_apply_patch_for_session_skips_future_prompts_for_same_file()
 
     let target = TargetPath::OutsideWorkspace("apply_patch_allow_session.txt");
     let (path, patch_path) = target.resolve_for_patch(&test);
+    let _path_cleanup = tempfile::TempPath::try_from_path(path.clone())?;
     let _ = fs::remove_file(&path);
 
     let patch_add = build_add_file_patch(&patch_path, "before");