These tests documented the macOS symlink bypass bug with
platform-conditional assertions. The fix and proper regression
tests are in PR #61 (tests/tools/test_write_deny.py), so remove
them here to avoid ordering conflicts between the two PRs.
- Renamed test method for clarity and added comprehensive tests for `SessionSource` including handling of numeric `chat_id`, missing optional fields, and invalid platforms.
- Introduced tests for session source descriptions based on chat types and names, ensuring accurate representation in prompts.
- Improved file tools tests by validating schema structures, ensuring no duplicate model IDs, and enhancing error handling in file operations.