Add unit tests for Annotation.resolve()

[jc-macdonald]

Summary

Unit tests for Annotation.resolve() covering dict-based and callable-based resolution, plus error paths.

Closes #3

Changes

• Dict lookup: resolves correct value for a given config key
• Dict lookup (all keys): iterates all entries to confirm correctness
• Callable lookup: lambda-based resolution returns expected value
• Float coercion: confirms resolve() returns float even when callable returns int
• Missing config key: raises KeyError when the config dict lacks the annotation key
• Missing lookup key: raises KeyError when the lookup dict lacks the resolved value

Stats

• 6 new tests (26 total)
• protocols.py coverage: 91% → 100%
• Total coverage: 55.73% → 60.41%
• just ci passes (format, lint, mypy strict, coverage)