feat(PBI-74): cleanup oude sprint-store (Story 9 / T-883)

- rm stores/sprint-store.ts — alle componenten lezen nu via
  useSprintWorkspaceStore (T-881 voltooide imports-migratie)
- update SprintHydrationWrapper-comment: schaduw-fase referenties
  verwijderd

Verify: 671 tests groen, typecheck clean, build groen.
Grep useSprintStore = 0.

components/sprint/sprint-hydration-wrapper.tsx

@@ -1,12 +1,10 @@
 'use client'
 
-// PBI-74 / Story 9 / T-880: Sprint workspace hydration wrapper.
+// PBI-74 / Story 9: Sprint workspace hydration wrapper.
 //
 // Server-component (sprint page) fetcht initial sprint snapshot; deze wrapper
 // hydreert useSprintWorkspaceStore op client-mount, mount de SSE-hook en de
-// resync-laag. Tijdens T-880 (schaduw-fase) blijft useSprintStore parallel
-// werken in sprint-board components — beide stores naast elkaar tot T-881
-// componenten omzet en T-883 de oude store opruimt.
+// resync-laag.
 
 import { useEffect, useRef } from 'react'
 import { useSprintRealtime } from '@/lib/realtime/use-sprint-realtime'

stores/sprint-store.ts

@@ -1,57 +0,0 @@
-import { create } from 'zustand'
-
-interface SprintStore {
-  // sprintId → storyId[]
-  sprintStoryOrder: Record<string, string[]>
-  // storyId → taskId[]
-  taskOrder: Record<string, string[]>
-
-  initSprint: (sprintId: string, storyIds: string[]) => void
-  addStoryToSprint: (sprintId: string, storyId: string) => void
-  removeStoryFromSprint: (sprintId: string, storyId: string) => void
-  reorderSprintStories: (sprintId: string, storyIds: string[]) => void
-  rollbackSprint: (sprintId: string, storyIds: string[]) => void
-
-  initTasks: (storyId: string, taskIds: string[]) => void
-  reorderTasks: (storyId: string, taskIds: string[]) => void
-  rollbackTasks: (storyId: string, taskIds: string[]) => void
-}
-
-export const useSprintStore = create<SprintStore>((set) => ({
-  sprintStoryOrder: {},
-  taskOrder: {},
-
-  initSprint: (sprintId, storyIds) =>
-    set((s) => ({ sprintStoryOrder: { ...s.sprintStoryOrder, [sprintId]: storyIds } })),
-
-  addStoryToSprint: (sprintId, storyId) =>
-    set((s) => ({
-      sprintStoryOrder: {
-        ...s.sprintStoryOrder,
-        [sprintId]: [...(s.sprintStoryOrder[sprintId] ?? []), storyId],
-      },
-    })),
-
-  removeStoryFromSprint: (sprintId, storyId) =>
-    set((s) => ({
-      sprintStoryOrder: {
-        ...s.sprintStoryOrder,
-        [sprintId]: (s.sprintStoryOrder[sprintId] ?? []).filter((id) => id !== storyId),
-      },
-    })),
-
-  reorderSprintStories: (sprintId, storyIds) =>
-    set((s) => ({ sprintStoryOrder: { ...s.sprintStoryOrder, [sprintId]: storyIds } })),
-
-  rollbackSprint: (sprintId, storyIds) =>
-    set((s) => ({ sprintStoryOrder: { ...s.sprintStoryOrder, [sprintId]: storyIds } })),
-
-  initTasks: (storyId, taskIds) =>
-    set((s) => ({ taskOrder: { ...s.taskOrder, [storyId]: taskIds } })),
-
-  reorderTasks: (storyId, taskIds) =>
-    set((s) => ({ taskOrder: { ...s.taskOrder, [storyId]: taskIds } })),
-
-  rollbackTasks: (storyId, taskIds) =>
-    set((s) => ({ taskOrder: { ...s.taskOrder, [storyId]: taskIds } })),
-}))