Use verified contracts release during development

[woksin]

Added

• Resolve cratis-chronicle-contracts 16.38.2 from the verified Chronicle GitHub release asset until PyPI Trusted Publishing is configured.
• Pin the release asset by SHA-256 and smoke-test an event message, service stub, and protobuf-net Guid import.
• Document the temporary distribution and the tracked migration to PyPI.

Why

The generated contracts package is ready, but the official PyPI publication remains blocked on Chronicle repository admin access and PyPI Trusted Publisher setup. Hosting the verified wheel on the matching Chronicle release lets contributors install Chronicle.Python normally and continue issues #2, #3, and #4 without copying generated files or waiting for that external administration.

The wheel was built from the committed Source/Kernel/Protobuf schemas at exact tag v16.38.2. Its downloaded SHA-256 is 357052da8a62653dcfa40c8051c4af2c6a6d29295cb6783f59dd5efdf4bdc3f9.

Verification

• ruff format --check .
• ruff check .
• mypy src
• pytest — 2 passed
• python -m build
• python -m twine check dist/*
• markdownlint-cli2 — 0 issues
• Clean environment installed cratis-chronicle-contracts==16.38.2 from the hash-pinned release URL and imported the generated event contract