Calendar · Agenda and people: an agenda, an event's details, its guests

AgendaView lists the days ahead under their names, whole days first,
then by the hour, and leaves out days with nothing; it rides on
lists::Sections, so a press or an arrow selects and Enter opens. An
empty stretch says nothing is planned.

EventPopover is an event's chip that opens its details: its title in
its hue, when and where, who is asked, and Edit and Delete when the
owner handles them. It opens through Popover::with_opener, which now
hands any element the toggle and keeps focus, placement and every way
out in the popover. AttendeeList counts the answers and lists each
guest with their answer, the organizer first. A hue worn in a row is
now data_display::color_mark, for mail labels and events alike.

TASKS.md

@@ -108,7 +108,7 @@ Per-component lines live in `tasks/`. Tags there:
 - [x] T29c Mail · Writing
 - [x] T29d Mail · Sorting
 - [x] T30a Calendar · Months
-- [ ] T30b Calendar · Time grid
+- [x] T30b Calendar · Time grid
 - [ ] T30c Calendar · Agenda and people
 - [ ] T30d Calendar · Editing
 - [ ] T31 Project — `tasks/ch31-43.md`
@@ -356,3 +356,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T29d | 3 | PASS | |
 | T30a | 1 | PASS | |
 | T30b | 1 | FAIL | the week and day views froze the line at now and today: the moment read once went down as given and turned the ticker off |
+| T30b | 2 | PASS | |