feat(PBI-74): sprint-workspace-store (Story 9) (#181)

* feat(PBI-74): sprint-workspace-store skelet (Story 9 / T-879)

- stores/sprint-workspace/{types,store,selectors,restore}.ts conform
  product-workspace blueprint
- ContextSlice: activeProduct, activeSprintId, activeStoryId, activeTaskId
- EntitiesSlice: sprintsById, storiesById, tasksById
- RelationsSlice: sprintIdsByProduct, storyIdsBySprint, taskIdsByStory
- LoadingSlice met activeRequestId voor race-safe ensure*Loaded
- SyncSlice: realtimeStatus, lastResyncAt, resyncReason
- Realtime applyRealtimeEvent voor sprint/story/task entities + unknown-event
  fallback, parent-move handling, child-cleanup bij D op sprint/story
- Optimistic mutations: sprint-story-order, sprint-task-order, entity-patch
- LocalStorage hints (storage key sprint-workspace-hints) per product/sprint
- 45 unit-tests groen — verplicht 13 cases uit workspace-store.md §Tests

* feat(PBI-74): sprint hydratie + realtime SSE (Story 9 / T-880)

- app/api/realtime/sprint/route.ts: SSE-stream LISTEN/NOTIFY op
  scrum4me_changes, filter entity ∈ {sprint, story, task} per product_id;
  ready-event, heartbeat 25s, hard-close 240s
- lib/realtime/use-sprint-realtime.ts: client-hook met backoff-reconnect;
  ready-cycle telt; geen close op hidden; setRealtimeStatus
- lib/realtime/use-sprint-workspace-resync.ts: visibility + online triggers
  resyncActiveScopes('visible' | 'reconnect')
- components/sprint/sprint-hydration-wrapper.tsx: hydrateSnapshot via
  useEffect met fingerprint-check; mount realtime + resync
- app/(app)/products/[id]/sprint/[sprintId]/page.tsx: wrap SprintBoardClient
  in SprintHydrationWrapper; bouw SprintWorkspaceTask-shape voor
  tasksByStoryWorkspace en SprintHydrationData voor de wrapper

Schaduw-fase: useSprintStore blijft parallel werken in board components
totdat T-881 die migreert en T-883 de oude store opruimt.

* feat(PBI-74): migreer sprint-board componenten naar workspace-store (Story 9 / T-881)

- TaskList: leest tasks via selectTasksForStory met useShallow; DnD via
  applyOptimisticMutation('sprint-task-order') + settle/rollback
- SprintBacklogLeft: leest stories via selectStoriesForActiveSprint met
  useShallow; props 'stories' verwijderd
- SprintBoardClient: leest sprintStories uit selector i.p.v. lokale state;
  add/remove via direct setState met manuele snapshot-rollback;
  reorder via applyOptimisticMutation('sprint-story-order'); assignee-
  change via store entity-mutation; tasksByStory en sprintStoryIdList
  props weg
- app/(app)/.../sprint/[sprintId]/page.tsx: bouwt SprintHydrationData voor
  wrapper; geeft alleen non-store props door aan SprintBoardClient

useSprintStore wordt nergens meer geïmporteerd — alleen comment-referentie
in SprintHydrationWrapper. Cleanup van het bestand zelf in T-883.

Verify groen (671 tests, typecheck, lint clean).

* feat(PBI-74): read-routes voor sprint-workspace + cache-headers (Story 9 / T-882)

- GET /api/products/[id]/sprints — lijst sprints per product
  (ensureProductSprintsLoaded). force-dynamic, productAccessFilter,
  start_date/end_date naar ISO-date string.
- GET /api/sprints/[id]/workspace — sprint snapshot met sprint-meta,
  stories (incl. taskCount/doneCount/assignee), tasks gegroepeerd per
  story (ensureSprintLoaded). force-dynamic, productAccessFilter via
  product, status-vertaling via taskStatusToApi/storyStatusToApi.

Race-safe loaders (activeRequestId-guard), restore-flow (cascade-restore
via writeProductHint/writeSprintHint/writeStoryHint/writeTaskHint),
resync-laag (useSprintWorkspaceResync visibility + online), unknown-event
filter (isUnknownEntityEvent → resyncActiveScopes('unknown-event')) zijn
allemaal in T-879/T-880 al ingebouwd; T-882 sluit het loop met de
ontbrekende API-endpoints + cache-headers (cache: 'no-store' op fetches,
force-dynamic op routes).

* 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.

* docs(PBI-74): update Story 9 status in implementatieplan (T-884)

- Frontmatter: ready-to-execute → in-progress; revision 1 → 2;
  last_updated 2026-05-09 → 2026-05-10
- Stories-tabel: kolom Status toegevoegd (Stories 1-8 DONE via PR #180,
  Story 9 met T-884 op review)
- §Story 9: per-taak status + acceptatie-checklist voor T-884 manuele
  staging-checks
- Aanbeveling-blokje: noteert dat Story 9 vroeger gestart is dan het
  ontwerpdoc adviseerde

docs/INDEX.md

@@ -62,7 +62,7 @@ Auto-generated on 2026-05-10 from front-matter and headings.
 | [Tweede Claude Agent — Planning Agent](./plans/tweede-claude-agent-planning.md) | proposal | 2026-05-03 |
 | [Scrum4Me — v1.0 readiness](./plans/v1-readiness.md) | active | 2026-05-04 |
 | [Zustand store rearchitecture - active context, realtime en resync](./plans/zustand-store-rearchitecture.md) | ready-to-execute | 2026-05-09 |
-| [Zustand workspace-store implementatieplan (PBI-74)](./plans/zustand-workspace-store-implementation.md) | ready-to-execute | 2026-05-09 |
+| [Zustand workspace-store implementatieplan (PBI-74)](./plans/zustand-workspace-store-implementation.md) | in-progress | 2026-05-10 |
 
 ### Archive