Several publish-rejection and validation behaviors for schema epochs are not covered in the Python test suite. The existing tests in test_layered_schema07.py, test_layered_schema10.py, and test_layered_schema11.py cover the happy path but leave gaps in error handling and follower-side publish constraints.

Add test cases to the identified files:

test_layered_schema07.py:

• Publish the same URI at epoch E2 after it was already published at a later epoch E1; verify publish epochs for the same URI cannot regress.

test_layered_schema10.py:

• Publish a follower-created table with schema epoch 0; verify EINVAL.
• Publish a follower-created table at epoch <= stable schema epoch; verify rejection once stable is set.
• Call publish on a follower-created table without schema_epoch; verify no-op.
• Leave an unpublished table in a state that would otherwise become stable; verify the illegal state fails loudly.
• Trigger illegal unpublished-table stable-data case; verify no partial durable metadata is produced.

test_layered_schema11.py:

• Publish a follower drop with schema epoch 0; verify EINVAL.
• Publish a follower drop at epoch <= stable schema epoch; verify rejection.
• Call publish on a follower drop without schema_epoch; verify no-op.