feat(PBI-74): oude stores opruimen (Story 8)

Workspace-store is nu de enige bron voor product-backlog client-state. De
vier voorgangers en de dual-dispatch-infrastructuur zijn verwijderd.

- T-872: grep over codebase op useBacklogStore/usePlannerStore/
  useSelectionStore/useProductStore is leeg.
- T-873..T-876: stores/{backlog,planner,selection,product}-store.ts deleted.
- T-877: __tests__/realtime/payload-contract.test.ts en
  __tests__/api/backlog-realtime.test.ts deleted — pbi/story/task I|U|D
  payload-handling wordt al gedekt door
  __tests__/stores/product-workspace/store.test.ts (incl. parent-move,
  idempotent inserts, delete-cleanup).
- T-878: lib/realtime/dev-workspace-fingerprint.ts deleted, dual-dispatch
  uit BacklogHydrationWrapper en lib/realtime/use-backlog-realtime.ts
  weggehaald. stores/products-store.ts (lijst van producten ≠ active
  product) blijft ongewijzigd.

Bijwerkingen:
- BacklogPbi en BacklogStory types in components/backlog/story-panel.tsx en
  components/sprint/sprint-backlog.tsx krijgen sort_order zodat ze met de
  workspace-types overeenkomen.
- Server-pages /products/[id]/page.tsx (desktop+mobile) en
  /products/[id]/sprint/[sprintId]/page.tsx selecteren sort_order op story
  en mappen het door in de hydration-payload.

Verify: lint+typecheck clean, 626/626 tests groen (verlies van 25 redundante
oude-store tests; workspace-store tests dekken hetzelfde gedrag).

Refs: PBI-74, ST-1325, T-872..T-878

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/backlog/backlog-hydration-wrapper.tsx

@@ -1,17 +1,15 @@
 'use client'
 
 import { useEffect, useRef } from 'react'
-import { useBacklogStore, type BacklogPbi, type BacklogStory, type BacklogTask } from '@/stores/backlog-store'
 import { useBacklogRealtime } from '@/lib/realtime/use-backlog-realtime'
 import { useWorkspaceResync } from '@/lib/realtime/use-workspace-resync'
 import { useProductWorkspaceStore } from '@/stores/product-workspace/store'
 import type {
-  BacklogPbi as WorkspacePbi,
-  BacklogStory as WorkspaceStory,
-  BacklogTask as WorkspaceTask,
+  BacklogPbi,
+  BacklogStory,
+  BacklogTask,
   ProductBacklogSnapshot,
 } from '@/stores/product-workspace/types'
-import { logWorkspaceFingerprint } from '@/lib/realtime/dev-workspace-fingerprint'
 
 interface InitialData {
   pbis: BacklogPbi[]
@@ -37,11 +35,7 @@ function fingerprint(data: InitialData): string {
   return `${pbiPart}|${storyPart}|${taskPart}`
 }
 
-// PBI-74 / T-844: dual-dispatch — naast de oude useBacklogStore vullen we nu
-// ook de nieuwe product-workspace-store. De oude store blijft tijdelijk
-// leidend voor componenten; in Story 3 verschuiven consumers één voor één.
-// De runtime-payload bevat sort_order op PBI/Story (Prisma schema), ook al
-// staat het niet op het oude InitialData type — daarom de cast hieronder.
+// PBI-74 / Story 8: workspace-store is nu enige bron — dual-dispatch weg.
 function toWorkspaceSnapshot(
   data: InitialData,
   productId: string,
@@ -49,9 +43,9 @@ function toWorkspaceSnapshot(
 ): ProductBacklogSnapshot {
   return {
     product: { id: productId, name: productName ?? '' },
-    pbis: data.pbis as unknown as WorkspacePbi[],
-    storiesByPbi: data.storiesByPbi as unknown as Record<string, WorkspaceStory[]>,
-    tasksByStory: data.tasksByStory as unknown as Record<string, WorkspaceTask[]>,
+    pbis: data.pbis,
+    storiesByPbi: data.storiesByPbi,
+    tasksByStory: data.tasksByStory,
   }
 }
 
@@ -61,21 +55,17 @@ export function BacklogHydrationWrapper({
   productName,
   children,
 }: BacklogHydrationWrapperProps) {
-  const setInitialData = useBacklogStore((s) => s.setInitialData)
   const lastFingerprint = useRef<string>('')
 
   useEffect(() => {
     const fp = fingerprint(initialData)
     if (fp !== lastFingerprint.current) {
       lastFingerprint.current = fp
-      setInitialData(initialData)
-      // Dual-dispatch: nieuwe workspace-store schaduwt mee.
       useProductWorkspaceStore
         .getState()
         .hydrateSnapshot(toWorkspaceSnapshot(initialData, productId, productName))
-      logWorkspaceFingerprint('hydrate')
     }
-  }, [initialData, productId, productName, setInitialData])
+  }, [initialData, productId, productName])
 
   useBacklogRealtime(productId)
   useWorkspaceResync()

components/backlog/story-panel.tsx

@@ -56,6 +56,7 @@ export interface Story {
   description: string | null
   acceptance_criteria: string | null
   priority: number
+  sort_order: number
   status: string
   pbi_id: string
   sprint_id: string | null

components/sprint/sprint-backlog.tsx

@@ -45,6 +45,7 @@ export interface SprintStory {
   sprint_id: string | null
   created_at: Date
   priority: number
+  sort_order: number
   status: string
   taskCount: number
   doneCount: number