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
Madhura68
fdd83005a8