Automate reverse sync of Python SDK README version updates

[coderabbitai]

Summary

The generator sync in python-sdk#307 regressed the Python SDK README version.

Add reverse-sync automation so generated README version content remains consistent with SDK releases.

Required changes

• Determine whether the SDK README version can be managed entirely by release-please.
• If release-please cannot manage it, add a workflow that opens a pull request in openfga/sdk-generator when a Python SDK release pull request is created.
• Update the generator template or configuration from that pull request.
• Keep unrelated README whitespace changes out of the version synchronization workflow.

Related work

SDK tracking issue: openfga/python-sdk#308

References

• Pull request: chore(sync): sync with generator python-sdk#307
• Review: chore(sync): sync with generator python-sdk#307 (review)
• Requested by: @SoulPancake

Acceptance criteria

• A Python SDK release updates the generator-owned README version automatically, or release-please is the documented and enforced owner.
• A subsequent generator sync does not regress the Python SDK README version.
• The workflow has automated coverage or validation for the regression case.