Stage publishable Python runtime wheels (#18865)

This is PR 2 of the Python SDK PyPI publishing split. [PR
1](https://github.com/openai/codex/pull/18862) refreshed the generated
SDK bindings; this PR makes the runtime package itself publishable, and
PR 3 will wire the SDK package/version pinning to this runtime package.

## Summary
- Rename the runtime distribution to `openai-codex-cli-bin` while
keeping the import package as `codex_cli_bin`.
- Make the runtime package wheel-only and build `py3-none-<platform>`
wheels instead of interpreter-specific wheels.
- Add `stage-runtime --codex-version` and `--platform-tag` so release
staging can produce the platform wheel matrix from Codex release tags.
- Add focused artifact workflow tests for version normalization,
platform tag injection, and runtime wheel metadata.

## Why Rename
There is already an unofficial PyPI package,
[`codex-bin`](https://pypi.org/project/codex-bin/), distributing OpenAI
Codex binaries. Publishing the official SDK runtime dependency as
`openai-codex-cli-bin` makes the ownership clear, avoids confusing the
SDK-pinned runtime wheel with that unowned wrapper, and keeps the import
package unchanged as `codex_cli_bin`.

## Tests
- `uv run --extra dev pytest
tests/test_artifact_workflow_and_binaries.py` -> 21 passed
- `uv run --extra dev python scripts/update_sdk_artifacts.py
stage-runtime /tmp/codex-python-pr2-rebased/runtime-stage
/tmp/codex-python-pr2-rebased/codex --codex-version
rust-v0.116.0-alpha.1 --platform-tag macosx_11_0_arm64`
- `uv run --with build --extra dev python -m build --wheel
/tmp/codex-python-pr2-rebased/runtime-stage`
- `uv run --with twine --extra dev twine check
/tmp/codex-python-pr2-rebased/runtime-stage/dist/openai_codex_cli_bin-0.116.0a1-py3-none-macosx_11_0_arm64.whl`

## Note
- Full `uv run --extra dev pytest` currently fails because regenerating
from schemas already on `main` adds new DeviceKey Python types. I left
that generated catch-up out of this runtime-only PR.

sdk/python-runtime/README.md

@@ -5,5 +5,5 @@ Platform-specific runtime package consumed by the published `codex-app-server-sd
 This package is staged during release so the SDK can pin an exact Codex CLI
 version without checking platform binaries into the repo.
 
-`codex-cli-bin` is intentionally wheel-only. Do not build or publish an sdist
-for this package.
+`openai-codex-cli-bin` is intentionally wheel-only. Do not build or publish an
+sdist for this package.

sdk/python-runtime/hatch_build.py

@@ -1,15 +1,30 @@
 from __future__ import annotations
 
+import os
+
 from hatchling.builders.hooks.plugin.interface import BuildHookInterface
 
 
+def _platform_tag() -> str:
+    from packaging.tags import sys_tags
+
+    return next(iter(sys_tags())).platform
+
+
 class RuntimeBuildHook(BuildHookInterface):
     def initialize(self, version: str, build_data: dict[str, object]) -> None:
         del version
         if self.target_name == "sdist":
             raise RuntimeError(
-                "codex-cli-bin is wheel-only; build and publish platform wheels only."
+                "openai-codex-cli-bin is wheel-only; build and publish platform wheels only."
             )
 
+        platform_tag = self.config.get("platform-tag") or os.environ.get(
+            "CODEX_CLI_BIN_PLATFORM_TAG"
+        )
+        if not isinstance(platform_tag, str) or not platform_tag:
+            platform_tag = _platform_tag()
+
         build_data["pure_python"] = False
-        build_data["infer_tag"] = True
+        build_data["infer_tag"] = False
+        build_data["tag"] = f"py3-none-{platform_tag}"

sdk/python-runtime/pyproject.toml

@@ -3,7 +3,7 @@ requires = ["hatchling>=1.24.0"]
 build-backend = "hatchling.build"
 
 [project]
-name = "codex-cli-bin"
+name = "openai-codex-cli-bin"
 version = "0.0.0-dev"
 description = "Pinned Codex CLI runtime for the Python SDK"
 readme = "README.md"

sdk/python-runtime/src/codex_cli_bin/__init__.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import os
 from pathlib import Path
 
-PACKAGE_NAME = "codex-cli-bin"
+PACKAGE_NAME = "openai-codex-cli-bin"
 
 
 def bundled_codex_path() -> Path: