Adds a -m/--minutes flag to `streamd timesheet` that displays time
in HH:MM format (e.g., 8:30) instead of decimal hours (e.g., 8.5h).
Includes unit tests for both formatting functions.
Implement smoother todo editing with the following features:
- Display numbered tasks [1], [2], etc. in `streamd todo`
- Add `streamd todo N edit` to open editor at task line
- Add `streamd todo N done` to insert @Done after @Task
- Add `--show-future` flag to include future tasks (hidden by default)