Adds two independent display settings under Settings › Appearance, both
defaulting to the current behaviour (off) so nothing changes until a user
opts in:
• Agenda › "Past events" (Show / Dim / Hide) — events that already ended
today can be left as-is, faded, or dropped from the list. Hiding also
removes any day left empty, falling back to the empty state. Re-evaluated
each minute so rows fade/fall away as they end while the screen is open.
• Calendar › "Dim completed events" — a separate toggle that fades finished
events in the month and week grids, kept independent of the agenda setting.
An event counts as completed once its end is at or before now (in-progress
events are never dimmed; all-day events only after their day is fully over),
via a shared EventInstance.hasEnded(now). The grids read the cut-off through
a new LocalDimCutoff CompositionLocal (mirroring LocalShowHourLines) so only
the event chips recompose on the per-minute tick, and only while dimming is on.
Also adds an "Agenda" section header so the agenda rows stand apart in the
now-busier Appearance screen, and documents the feature in the changelog.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>