- Add `simple_weekly` type and `weekly` field to `rem` record
- Add `exdate` field to `rem` for excluded dates
- Add `collect_exdates` collector to pipeline
- implement weekly `RRULE` handling with `BYDAY`, `INTERVAL`,
`COUNT`/`UNTIL`
- Add `render_weekly` to emit one `REM` per weekday with `UNTIL`/`*N`
- Replace `timedesc_of_date_or_datetime` with
`timedesc_of_utc_or_timestamp_local` in utils
- Refactor `get_exdates`/`get_rdates` to separate dates, datetimes and
periods; add debug logging per UID
- Wrap reminder output in try/catch in main; drop trailing newline
duplication
- Mark implemented predicates (P00–P05, P09, P12, P14) with ✅;
remove P18–P20 (ignored/deferred)
