[codex] Stage Python SDK beta versions from release tags (#24872)

## Summary
- Treat `sdk/python` as a development template with source version
`0.0.0-dev`, matching the existing Python runtime packaging pattern.
- Have `python-v*` tags supply the published SDK beta version through
the existing `stage-sdk --sdk-version` path.
- Remove the workflow check requiring a source version bump for each
beta release and remove its now-unused host Python setup step.
- Keep the reviewed runtime dependency pin at
`openai-codex-cli-bin==0.132.0`.
- Remove beta-number-specific documentation so it does not need editing
for each publish.

## Why
The package staging script already writes the release version into the
artifact. Requiring the checked-in SDK template version to match every
tag adds release-only source churn without changing the package users
receive.

## Validation
- Not run locally; relying on online CI for this workflow and metadata
change.

## Release
After this PR lands, publish the next beta by pushing tag
`python-v0.1.0b2` from merged `main`.

.github/workflows/python-sdk-release.yml

@@ -23,11 +23,6 @@ jobs:
         with:
           persist-credentials: false
 
-      - name: Setup Python
-        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
-        with:
-          python-version: "3.12"
-
       - name: Validate tag and build Python SDK package
         shell: bash
         run: |
@@ -39,14 +34,6 @@ jobs:
             exit 1
           fi
 
-          configured_version="$(
-            python -c 'import tomllib; print(tomllib.load(open("sdk/python/pyproject.toml", "rb"))["project"]["version"])'
-          )"
-          if [[ "${configured_version}" != "${sdk_version}" ]]; then
-            echo "Tag version ${sdk_version} does not match sdk/python/pyproject.toml version ${configured_version}."
-            exit 1
-          fi
-
           # The pinned runtime currently publishes a musllinux Linux wheel.
           # Build in Alpine so release type generation installs that wheel.
           docker run --rm \