chore: bump version to 0.9.0dev5

[rlippmann]

What changed

• Bumped the development release version.
• Included the state opacity refactor:
  • removed the public raw state API (State, Engine.state, and state= construction);
  • moved consumers to semantic reads (premise / policies) and JSON persistence.
• Included policy identity normalization cleanup:
  • retained Unicode normalization, apostrophe normalization, case-insensitive matching, and whitespace normalization;
  • removed article stripping (a, an, the);
  • removed dont → don't rewriting.
• Updated tests and conformance fixtures to match the current public contract.
• Updated CI and contributor documentation to use the new uv development dependency group workflow.

Why

• Prepare the next development release after completing the state opacity migration.
• Align runtime behavior with the documented policy identity contract.
• Remove legacy normalization behavior that introduced language-specific transformations into identity matching.

Checklist

• pre-commit run (uv run pre-commit run --all-files)
• tests pass (uv run pytest)