fix: address P1 code quality issues from code review (#38)

- Fix TOCTOU vulnerabilities in documentation assessors by using try-except around file reads
- Replace regex-based type annotation detection with AST parsing to eliminate false positives
- Rename Assessment.attributes_skipped to attributes_not_assessed for semantic clarity
- Update all references in reporters, scanner, and tests

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Jeremy Eder <jeremyeder@users.noreply.github.com>

Author: jeremyeder