Check root Python script formatting in CI (#25165)

## Why

Python files under `scripts/` were not covered by the repository
formatting recipe or the CI formatting job, so formatting drift could
merge unnoticed.

## What

- Add a dedicated `scripts/pyproject.toml` and `scripts/uv.lock` so
root-script formatting uses a locked Ruff version.
- Extend `just fmt` to format root Python scripts and add
`fmt-scripts-check` for CI.
- Run `just fmt-scripts-check` from `.github/workflows/ci.yml`,
installing `uv` through SHA-pinned `astral-sh/setup-uv` while retaining
the `uv` `0.11.3` pin.
- Apply Ruff formatting to the root Python scripts, including
`scripts/just-shell.py`, and extend
`sdk/python/tests/test_artifact_workflow_and_binaries.py` to cover the
root formatting recipe.
- Update `AGENTS.md` so agents run `just fmt` after code changes
anywhere in the repository.

## Validation

- Extended the existing Python SDK workflow test to assert that `just
fmt` includes root Python scripts.

scripts/codex_package/archive.py

@@ -99,7 +99,9 @@ def resolve_zstd_command(
 
 
 def write_zip_archive(package_dir: Path, archive_path: Path) -> None:
-    with zipfile.ZipFile(archive_path, "w", compression=zipfile.ZIP_DEFLATED) as archive:
+    with zipfile.ZipFile(
+        archive_path, "w", compression=zipfile.ZIP_DEFLATED
+    ) as archive:
         for path in package_entries(package_dir):
             relative_path = path.relative_to(package_dir)
             if path.is_dir():
@@ -109,4 +111,7 @@ def write_zip_archive(package_dir: Path, archive_path: Path) -> None:
 
 
 def package_entries(package_dir: Path) -> list[Path]:
-    return sorted(package_dir.rglob("*"), key=lambda path: path.relative_to(package_dir).as_posix())
+    return sorted(
+        package_dir.rglob("*"),
+        key=lambda path: path.relative_to(package_dir).as_posix(),
+    )