TODO/DONE auto-mark done when all subtasks done

README.md

@@ -142,6 +142,12 @@ recolored -- only the badge.
   open-only filter, but reappears if you clear the filter (or use the "Board: show all tasks" filter).
 - With that option **off**, the badge is an independent marker stored in task metadata
   (`organon_done`) that never touches the open/closed status.
+- **Auto-mark on subtasks (opt-in).** When every subtask on a card is completed, the badge flips to
+  Done automatically (honoring the mode above -- marker or close). It only nudges at the moment the
+  last subtask completes: recomputing all-done on each subtask change and acting only on the
+  not-all-done -> all-done transition, so if you then set the badge back to Todo it is respected (the
+  subtasks stay done -- the description may hold unfinished business). It never auto-reverts to Todo.
+  Off by default; enable it in the Done badge settings.
 - **Bulk per-column action.** The board column header dropdown gains a **Mark all as Done/Todo** entry
   (`Template/board/mark_all_item.php`, moved into the menu by `relocate.js`). It opens a single modal
   that both confirms and picks the direction -- **Mark all Done** or **Mark all Todo** -- then sets