fix(sections): a section can hold more than one task

Reported as "sections can only have one task", and that is exactly what it looked
like.

TaskList read the dragged task from its own `draggingId`, which is only set when
the drag *started* in that list. A task dragged in from the unsectioned rows above,
or from another section, arrived as null and the handler returned early — after it
had already called `stopPropagation`, so the section around it never got the drop
either.

So a section could only be dropped into while it was empty, because an empty one
has no row in the way to swallow the drop. Put one task in and there was no route
to a second. The id comes out of `dataTransfer` at drop time now, and `dragover`
decides with `carries()` rather than local state — which is the only thing a target
can read while a drag is in the air.

The stuck frame was the same cause: the section's own cleanup never ran, so the
highlight stayed lit after the drop. It is cleared on `dragend` now, which fires
once per drag on the source and bubbles to the window — the one place that is true
however a drag ends, including one abandoned with Escape, which produces no drop at
all and left the frame standing too.

The smoke test drops a second task onto the row already in the section, which is
the gesture that did nothing, and runs in WebKit as well.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/lib/components/TaskList.svelte

@@ -12,8 +12,9 @@
 	 * drawn where the row would land.
 	 */
 	import { app } from '$lib/stores.svelte.js';
+	import { t } from '$lib/i18n.svelte.js';
 	import { api } from '$lib/api.js';
-	import { TASK, startDrag, carries, accept } from '$lib/dnd.js';
+	import { TASK, startDrag, carries, dragged, accept } from '$lib/dnd.js';
 	import TaskRow from './TaskRow.svelte';
 
 	let { tasks, projectId, sectionId = '', canEdit = true } = $props();
@@ -33,7 +34,12 @@
 	}
 
 	function onDragOver(event, task) {
-		if (!canEdit || !carries(event, TASK) || !draggingId || draggingId === task.id) return;
+		// `carries` rather than `draggingId`: a task dragged from another list — the
+		// unsectioned rows above, or another section — never called this component's
+		// own dragstart, so its `draggingId` is null. Refusing on that made every
+		// list reject everything that came from outside it, which is the whole point
+		// of dragging between them.
+		if (!canEdit || !carries(event, TASK) || draggingId === task.id) return;
 		accept(event);
 
 		// Which half of the row the pointer is in decides the gap. Comparing against
@@ -54,13 +60,22 @@
 		// gesture and for sections with no rows to aim at. A drop that landed on a
 		// row has already said exactly where it goes, so it stops here.
 		event.stopPropagation();
-		const id = draggingId;
+		// From the drag itself, not from `draggingId`, which is only set when the
+		// drag *started* in this list. A task dragged in from the unsectioned rows
+		// or another section left it null, so this returned early — and it had
+		// already called stopPropagation, so the section around it never got the
+		// drop either. The result: a task could only be dropped into a section with
+		// no rows in it to aim at, which made every section look like it could hold
+		// exactly one task.
+		const id = dragged(event, TASK) || draggingId;
 		const below = overBelow;
 		draggingId = null;
 		overId = null;
 		if (!id || !canEdit || id === target.id) return;
 
 		const ordered = [...tasks].sort((a, b) => a.sort_order - b.sort_order);
+		// The dragged task may not be in this list at all — that is the cross-list
+		// case — so `without` is "this list minus it" either way.
 		const without = ordered.filter((t) => t.id !== id);
 		const at = without.findIndex((t) => t.id === target.id);
 		if (at < 0) return;
@@ -101,7 +116,7 @@
 			);
 		} catch {
 			app.replace(id, previous);
-			app.toast('Kunne ikke flytte opgaven.');
+			app.toast(t('task.moveFailed'));
 		}
 	}
 

web/src/lib/locales/da.js

@@ -587,5 +587,7 @@ export const da = {
 
 	'view.done': 'Færdige',
 	'view.showDone': 'Vis færdige',
-	'view.hideDone': 'Skjul færdige'
+	'view.hideDone': 'Skjul færdige',
+
+	'task.moveFailed': 'Kunne ikke flytte opgaven.'
 };

web/src/lib/locales/en.js

@@ -582,5 +582,7 @@ export const en = {
 
 	'view.done': 'Done',
 	'view.showDone': 'Show done',
-	'view.hideDone': 'Hide done'
+	'view.hideDone': 'Hide done',
+
+	'task.moveFailed': 'The task could not be moved.'
 };