[codex] Add independent beta release for the Python SDK (#24828)

## Why

`openai-codex` needs a beta release lifecycle without requiring beta
releases of its pinned runtime package. Previously, SDK staging rewrote
its runtime dependency to the SDK version, which made an SDK-only beta
impossible.

## What changed

- Set the initial SDK beta version to `0.1.0b1` and pin it to published
stable `openai-codex-cli-bin==0.132.0`.
- Decoupled SDK release staging from runtime versioning so it preserves
the reviewed exact runtime pin.
- Added a `python-v*` tag workflow that builds and publishes only
`openai-codex` through PyPI trusted publishing.
- Removed the Beta classifier from runtime package metadata for future
runtime publications.
- Regenerated protocol-derived SDK models from the selected stable
runtime package.

`0.132.0` is the newest stable runtime admitted by the checked-in
dependency date fence and retains the Linux wheel family currently used
by SDK CI.

## Release setup

Before pushing `python-v0.1.0b1`, configure PyPI trusted publishing for
the `openai-codex` project with workflow `python-sdk-release.yml`,
environment `pypi`, and job `publish-python-sdk`.

## Validation

- `uv run --frozen --extra dev ruff check src/openai_codex scripts
examples tests`
- Parsed `.github/workflows/python-sdk-release.yml` with PyYAML.
- Built staged release artifacts locally:
`openai_codex-0.1.0b1-py3-none-any.whl` and
`openai_codex-0.1.0b1.tar.gz`.
- Verified wheel metadata pins `openai-codex-cli-bin==0.132.0`.
- Tests are deferred to online CI for this PR.

sdk/python/README.md

@@ -16,8 +16,8 @@ uv sync
 source .venv/bin/activate
 ```
 
-Published SDK builds pin an exact `openai-codex-cli-bin` runtime dependency
-with the same version as the SDK. Pass `CodexConfig(codex_bin=...)` only
+Published SDK builds pin an exact compatible `openai-codex-cli-bin` runtime
+dependency. Pass `CodexConfig(codex_bin=...)` only
 when you intentionally want to run against a specific local app-server binary.
 
 ## Quickstart
@@ -111,7 +111,7 @@ python examples/01_quickstart_constructor/async.py
 
 Published SDK builds are pinned to an exact `openai-codex-cli-bin` package
 version, and that runtime package carries the platform-specific binary for the
-target wheel. The SDK package version and runtime package version must match.
+target wheel. SDK beta releases are versioned independently of runtime releases.
 
 ## Compatibility and versioning
 
@@ -119,7 +119,7 @@ target wheel. The SDK package version and runtime package version must match.
 - Runtime package: `openai-codex-cli-bin`
 - Python: `>=3.10`
 - Target protocol: Codex `app-server` JSON-RPC v2
-- Versioning rule: the SDK package version is the underlying Codex runtime version
+- Versioning rule: SDK releases pin one exact compatible Codex runtime version
 
 ## Notes