feat(backlog): add TaskPanel with sortable rows and TaskDialog wiring

Reads selectedStoryId + tasksByStory from stores. DnD reorder via
reorderTasksAction. Row click → ?editTask, + button → ?newTask&storyId.
DemoTooltip on drag handles and + button.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/backlog/task-panel.tsx

@@ -0,0 +1,196 @@
+'use client'
+
+import { useRouter } from 'next/navigation'
+import { useTransition } from 'react'
+import {
+  DndContext, DragEndEvent,
+  KeyboardSensor, PointerSensor, useSensor, useSensors, closestCenter,
+} from '@dnd-kit/core'
+import {
+  SortableContext, sortableKeyboardCoordinates,
+  useSortable, verticalListSortingStrategy,
+} from '@dnd-kit/sortable'
+import { CSS } from '@dnd-kit/utilities'
+import { GripVertical, Plus } from 'lucide-react'
+import { toast } from 'sonner'
+import { useSelectionStore } from '@/stores/selection-store'
+import { useBacklogStore, type BacklogTask } from '@/stores/backlog-store'
+import { reorderTasksAction } from '@/actions/tasks'
+import { Button } from '@/components/ui/button'
+import { DemoTooltip } from '@/components/shared/demo-tooltip'
+import { EmptyPanel } from './empty-panel'
+import { PRIORITY_BORDER } from './backlog-card'
+import { cn } from '@/lib/utils'
+
+const STATUS_COLORS: Record<string, string> = {
+  TO_DO: 'bg-status-todo/15 text-status-todo border-status-todo/30',
+  IN_PROGRESS: 'bg-status-in-progress/15 text-status-in-progress border-status-in-progress/30',
+  REVIEW: 'bg-status-review/15 text-status-review border-status-review/30',
+  DONE: 'bg-status-done/15 text-status-done border-status-done/30',
+}
+const STATUS_LABELS: Record<string, string> = {
+  TO_DO: 'To Do',
+  IN_PROGRESS: 'Bezig',
+  REVIEW: 'Review',
+  DONE: 'Klaar',
+}
+
+function SortableTaskRow({
+  task,
+  isDemo,
+  onClick,
+}: {
+  task: BacklogTask
+  isDemo: boolean
+  onClick: () => void
+}) {
+  const { attributes, listeners, setNodeRef, transform, transition, isDragging } =
+    useSortable({ id: task.id })
+
+  return (
+    <div
+      ref={setNodeRef}
+      style={{ transform: CSS.Transform.toString(transform), transition }}
+      className={cn(
+        'flex items-center gap-2 px-3 py-2 rounded-lg border cursor-pointer',
+        'bg-surface-container hover:bg-surface-container-high transition-colors',
+        PRIORITY_BORDER[task.priority],
+        isDragging && 'opacity-50 shadow-lg',
+      )}
+      onClick={onClick}
+    >
+      <DemoTooltip show={isDemo}>
+        <button
+          {...attributes}
+          {...listeners}
+          disabled={isDemo}
+          onClick={(e) => e.stopPropagation()}
+          className="text-muted-foreground hover:text-foreground cursor-grab disabled:opacity-30 disabled:cursor-not-allowed shrink-0"
+          aria-label="Versleep om te herordenen"
+        >
+          <GripVertical className="size-4" />
+        </button>
+      </DemoTooltip>
+
+      <span className="flex-1 text-sm truncate">{task.title}</span>
+
+      <span
+        className={cn(
+          'text-xs px-1.5 py-0.5 rounded border shrink-0',
+          STATUS_COLORS[task.status] ?? STATUS_COLORS.TO_DO,
+        )}
+      >
+        {STATUS_LABELS[task.status] ?? task.status}
+      </span>
+    </div>
+  )
+}
+
+interface TaskPanelProps {
+  productId: string
+  isDemo: boolean
+  closePath: string
+}
+
+export function TaskPanel({ productId, isDemo, closePath }: TaskPanelProps) {
+  const router = useRouter()
+  const [, startTransition] = useTransition()
+  const selectedStoryId = useSelectionStore((s) => s.selectedStoryId)
+  const tasksByStory = useBacklogStore((s) => s.tasksByStory)
+
+  const tasks = selectedStoryId ? (tasksByStory[selectedStoryId] ?? []) : null
+
+  const sensors = useSensors(
+    useSensor(PointerSensor),
+    useSensor(KeyboardSensor, { coordinateGetter: sortableKeyboardCoordinates }),
+  )
+
+  function handleDragEnd(event: DragEndEvent) {
+    if (!selectedStoryId) return
+    const { active, over } = event
+    if (!over || active.id === over.id) return
+
+    const ids = tasks!.map((t) => t.id)
+    const from = ids.indexOf(active.id as string)
+    const to = ids.indexOf(over.id as string)
+    if (from === -1 || to === -1) return
+
+    const reordered = [...ids]
+    reordered.splice(from, 1)
+    reordered.splice(to, 0, active.id as string)
+
+    startTransition(async () => {
+      const result = await reorderTasksAction(selectedStoryId, reordered)
+      if (result?.error) toast.error(result.error)
+    })
+  }
+
+  const header = (
+    <div className="flex items-center justify-between px-4 py-3 border-b border-border bg-surface-container-low shrink-0">
+      <h2 className="text-sm font-medium">Taken</h2>
+      <DemoTooltip show={isDemo}>
+        <Button
+          size="sm"
+          variant="outline"
+          disabled={isDemo || !selectedStoryId}
+          onClick={() => {
+            if (!selectedStoryId) return
+            router.push(`${closePath}?newTask=1&storyId=${selectedStoryId}`)
+          }}
+        >
+          <Plus className="size-3.5 mr-1" />
+          Nieuwe taak
+        </Button>
+      </DemoTooltip>
+    </div>
+  )
+
+  if (tasks === null) {
+    return (
+      <div className="flex flex-col h-full">
+        {header}
+        <EmptyPanel message="Selecteer een story om de taken te bekijken." />
+      </div>
+    )
+  }
+
+  if (tasks.length === 0) {
+    return (
+      <div className="flex flex-col h-full">
+        {header}
+        <EmptyPanel
+          message="Nog geen taken voor deze story."
+          action={{
+            label: 'Nieuwe taak',
+            onClick: () => router.push(`${closePath}?newTask=1&storyId=${selectedStoryId}`),
+            disabled: isDemo,
+          }}
+        />
+      </div>
+    )
+  }
+
+  return (
+    <div className="flex flex-col h-full">
+      {header}
+      <div className="flex-1 overflow-y-auto p-3 space-y-1.5">
+        <DndContext
+          sensors={sensors}
+          collisionDetection={closestCenter}
+          onDragEnd={handleDragEnd}
+        >
+          <SortableContext items={tasks.map((t) => t.id)} strategy={verticalListSortingStrategy}>
+            {tasks.map((task) => (
+              <SortableTaskRow
+                key={task.id}
+                task={task}
+                isDemo={isDemo}
+                onClick={() => router.push(`${closePath}?editTask=${task.id}`)}
+              />
+            ))}
+          </SortableContext>
+        </DndContext>
+      </div>
+    </div>
+  )
+}