[5/8] Rename Python SDK package to openai-codex (#21905)

## Why

The SDK should publish under the reserved public distribution name
`openai-codex`, and its import module should match that name in the
Python style. Since package names can contain hyphens but import modules
cannot, the public import path becomes `openai_codex`.

Keeping the rename separate from the public API surface change makes the
naming change easy to review and avoids mixing it with API curation.

## What

- Rename the SDK distribution from `openai-codex-app-server-sdk` to
`openai-codex`.
- Rename the import package from `codex_app_server` to `openai_codex`.
- Keep the runtime wheel as the separate `openai-codex-cli-bin`
dependency.
- Update docs, examples, notebooks, artifact scripts, lockfile metadata,
and tests for the new distribution/module names.

## Stack

1. #21891 `[1/8]` Pin Python SDK runtime dependency
2. #21893 `[2/8]` Generate Python SDK types from pinned runtime
3. #21895 `[3/8]` Run Python SDK tests in CI
4. #21896 `[4/8]` Define Python SDK public API surface
5. This PR `[5/8]` Rename Python SDK package to `openai-codex`
6. #21910 `[6/8]` Add high-level Python SDK approval mode
7. #22014 `[7/8]` Add Python SDK app-server integration harness
8. #22021 `[8/8]` Add Python SDK Ruff formatting

## Verification

- Updated package metadata and public API tests to assert the
distribution and import names.

Co-authored-by: Codex <noreply@openai.com>

sdk/python/examples/_bootstrap.py

@@ -35,7 +35,7 @@ def ensure_local_sdk_src() -> Path:
     """Add sdk/python/src to sys.path so examples run without installing the package."""
     sdk_python_dir = _SDK_PYTHON_DIR
     src_dir = sdk_python_dir / "src"
-    package_dir = src_dir / "codex_app_server"
+    package_dir = src_dir / "openai_codex"
     if not package_dir.exists():
         raise RuntimeError(f"Could not locate local SDK package at {package_dir}")
 
@@ -49,7 +49,7 @@ def ensure_local_sdk_src() -> Path:
 
 def runtime_config():
     """Return an example-friendly AppServerConfig for repo-source SDK usage."""
-    from codex_app_server import AppServerConfig
+    from openai_codex import AppServerConfig
 
     ensure_runtime_package_installed(sys.executable, _SDK_PYTHON_DIR)
     return AppServerConfig()