Add EventSource enum and update SystemEvent in watcher.rs (M0 stub
updated to support Task 5 clean deletion). Create patterns.rs with
PatternFile/Pattern/MatchedEvent types, TOML loader, and classify()
matching against source + text. Five unit tests covering journald,
applog, no-match, and source discrimination cases.
- parse_id now strips both double and single quotes per os-release spec
- distro_family debian arm includes "mint" (legacy Linux Mint ID)
- Add tests: single-quoted ID round-trip, mint family classification
