[codex] Stage Python SDK beta versions from release tags

[aibrahim-oai]

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.