test(TaskDialog): cover wait/start/entry/end, recur, and annotations

[NaitikVerma6776]

Adds test coverage for TaskDialog's Wait/Start/End/Entry date fields, Recurrence editing,
and Annotations editing — the remaining gaps in #300 after #397/#395 already covered
row/dialog basics, priority, tags, project, depends, due date, complete/delete, UUID, pin,
and shortcuts.

No component changes — tests only, per the issue's guidance.

• Wait/Start/End/Entry: enable/save/cancel via test.each, plus Wait's empty-value case
  (uses ?? '' instead of || like the others)
• Recurrence: None display, existing value display, edit-mode seeding (empty vs existing),
  save, cancel-restore
• Annotations: empty state, existing list, edit mode copies (not mutates) task data,
  trimmed add on Enter, whitespace-only rejected, remove, save, cancel-restore

89/89 tests passing locally. Refs #300 (Tasks component still open, not closed by this PR).

[github-actions]

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