Replace Pyright with ty

[cgasgarth]

Summary

• replace the Python type-check dependency and CI/docs commands from Pyright to Astral's ty
• configure ty in pyproject.toml to match the current project baseline by checking server and shared, excluding server/tests, and suppressing stricter diagnostics that currently surface existing typing debt
• update the local typecheck script used by pre-commit so local hooks and CI run the same checker

Validation

• uv run ty check
• uv run pytest server/tests
• uv build
• uvx pre-commit run --all-files
• npm run check:e2e not run because this repo does not define that script