Verifies explicit allowlist keys, catch-all _API_KEY/_TOKEN patterns,
case insensitivity, TERMINAL_SSH prefix, and config.yaml routing for
non-secret keys. Covers the fix from PR #469.
- 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.
