feat(calendar): list due tasks from a task vdir beside the events

The sampler reads open VTODOs with a due date from
~/.local/share/tasks/<list>/*.ics (a vdirsyncer filesystem storage,
override with UDT_TASKS_DIR) and writes them to the cache as ISO
'task' lines. The card merges them into the week's rows by date, with
a checkbox before the title and an urgency colour: overdue critical,
due today warning, later label. Overdue tasks stay until done, so they
lead the table. Tasks never mark the month grid.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/README.md b/README.md
index 07171c2..e99ee68 100644
--- a/README.md
+++ b/README.md
@@ -131,6 +131,15 @@ every remaining day with an event while the rows stay the coming week. The card
 of the week defeats its own purpose. A cell too short for even one row draws
 the grid alone, without the legend, rather than a clipped half-row.
 
+**Tasks join the rows when a task vdir exists.** The sampler also reads
+open VTODOs with a due date from `~/.local/share/tasks/<list>/*.ics` (the
+layout a vdirsyncer `filesystem` storage writes; override the path with
+`UDT_TASKS_DIR`). They are merged into the rows by date, each with a checkbox
+before its title, coloured by urgency: overdue in `critical`, due today in
+`warning`, later in `label`. Overdue tasks stay listed until done, so they
+lead the table. Tasks never mark the grid, where colour means an appointment.
+Without the directory the card shows events only.
+
 **Calendar colours come from khal's own config**, parsed out of the
 `[calendars]` section by the sampler, then mapped onto the board's palette
 roles in `COLOUR_ROLE` at the top of `widgets/calendar.lua`: green to `ok`,