feat(todo): the Plan beside Upcoming, with what has no date (ADR 0033, D34)

Upcoming's 3-day grid gets the Plan Today's calendar has, through what
the two tabs now share (PlanHost). Its new last group holds the open
tasks of no day, so a week can be planned from the Inbox by dropping them
on an hour; they aren't counted on the button, which says what is due.

Whats-New: Upcoming's 3-day view has the Plan too, and tasks without a date can be dragged from it onto any day.
Whats-New-De: Auch die 3-Tage-Ansicht unter Demnächst hat den Plan, und Aufgaben ohne Datum lassen sich von dort auf jeden Tag ziehen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0033-halkyon-todo.md

@@ -730,6 +730,17 @@ The developer's review of 4 Nov 2026, again beside Todoist's screens.
     no more half hours. A tap that stops the day scrolling doesn't add, as a fling
     keeps pointers from what it scrolls.
 
+- **D34 The Plan beside Upcoming, with what has no date** (the developer's, 5 Nov 2026,
+  the agent's recommendation): the Plan (`PlanPanel`) stands beside Upcoming's 3-day
+  grid as beside Today's calendar, through what the two now share (`PlanHost`), a row
+  dropped on an hour or *All day* going to that day. It shows or hides for both calendars
+  (`TodayView.plan`, kept as it was: a second setting was the alternative, for a choice
+  people hardly make per tab); the projects picked are each tab's. It stays about today:
+  a block dropped on it loses its time only if it is today's. *No date*, its last
+  group, holds the open tasks of no day, sub-tasks staying with theirs, so that a week
+  is planned from the Inbox; it isn't in the button's count, which says what is due. A
+  routine's templates (the developer's idea) wait for what a routine is.
+
 ## Consequences
 
 - No email reminder, morning overview or evening review: the server can't read what is