Add strict typing to all scripts and tests

- All scripts and tests now pass pyright strict mode (0 errors)
- Add from __future__ import annotations for Python 3.9 compatibility
- Add proper type annotations to all functions
- Configure pyright with venv discovery for pytest types
- Fix CompletedProcess[str] return types in test helpers

The skill now dogfoods itself - eating our own cooking!

Add test suite with fixtures

Tests:
- test_init.py: 10 tests for init_typing.py script
- test_analyze.py: 8 tests for analyze_typing.py script
- All 18 tests passing

Fixtures:
- untyped/: 44 pyright errors (no type hints)
- partial/: 16 errors (some hints, Optional issues)
- third_party/: 11 errors (missing stubs scenario)

Fixes:
- Python 3.9 compatibility (from __future__ import annotations)
- analyze_typing.py: fix severity check ('error' not 1)