refactor: migrate stores to features/, remove dead packages, add modals + workspace sync
## Store migration (packages → features)
- Delete `packages/store/` — stores moved into web app's feature modules
- Delete `packages/hooks/` — replaced by feature-level hooks
- `features/issues/store.ts` — useIssueStore (was packages/store/issue-store)
- `features/inbox/store.ts` — useInboxStore (was packages/store/inbox-store)
- `features/workspace/store.ts` — absorbs agent state (was packages/store/agent-store)
- All imports updated from `@multica/store` → `@/features/*/store`
## Global modal system
- `features/modals/store.ts` — useModalStore (zustand)
- `features/modals/registry.tsx` — ModalRegistry renders active modal
- Mounted in app/layout.tsx alongside Toaster
- Create Workspace dialog now works (was broken: DropdownMenu ate click)
## Workspace real-time sync
- useRealtimeSync subscribes to workspace:updated, member:removed
- Member removal → auto-switch to another workspace
- Workspace settings update → sidebar reflects name change
- Workspace switch → parallel fetch issues + inbox + agents
## Bug fixes
- theme-provider: guard event.key for IME composition (isComposing check)
- task.go: publish comment:created + inbox:new events on task complete/fail
- listeners.go: broadcast comment:created, workspace:updated, member events
- events.go: add EventCommentUpdated, EventCommentDeleted constants
## Cleanup
- Remove _features/ tracking files (dev-only, not for main)
- Remove server/server binary from worktree
- Update CLAUDE.md to reflect new architecture
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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