[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/src/openai_codex/__init__.py

@@ -0,0 +1,65 @@
+from .client import AppServerConfig
+from .errors import (
+    AppServerError,
+    AppServerRpcError,
+    InternalRpcError,
+    InvalidParamsError,
+    InvalidRequestError,
+    JsonRpcError,
+    MethodNotFoundError,
+    ParseError,
+    RetryLimitExceededError,
+    ServerBusyError,
+    TransportClosedError,
+    is_retryable_error,
+)
+from .api import (
+    AsyncCodex,
+    AsyncThread,
+    AsyncTurnHandle,
+    Codex,
+    ImageInput,
+    Input,
+    InputItem,
+    LocalImageInput,
+    MentionInput,
+    RunResult,
+    SkillInput,
+    TextInput,
+    Thread,
+    TurnHandle,
+)
+from .retry import retry_on_overload
+from ._version import __version__
+
+__all__ = [
+    "__version__",
+    "AppServerConfig",
+    "Codex",
+    "AsyncCodex",
+    "Thread",
+    "AsyncThread",
+    "TurnHandle",
+    "AsyncTurnHandle",
+    "RunResult",
+    "Input",
+    "InputItem",
+    "TextInput",
+    "ImageInput",
+    "LocalImageInput",
+    "SkillInput",
+    "MentionInput",
+    "retry_on_overload",
+    "AppServerError",
+    "TransportClosedError",
+    "JsonRpcError",
+    "AppServerRpcError",
+    "ParseError",
+    "InvalidRequestError",
+    "MethodNotFoundError",
+    "InvalidParamsError",
+    "InternalRpcError",
+    "ServerBusyError",
+    "RetryLimitExceededError",
+    "is_retryable_error",
+]