feat(01-01): create Zustand store with 6 slices, IPC batcher, and unit tests

- Install zustand 5.x and immer 11.x dependencies
- Create 6 Zustand slices: navigation, company, selection, ui, communication, social
- Create combined store with devtools + immer middleware
- Create IPC event batcher with 50ms debounce window (schedule/flush/dispose)
- Create typed selector hooks for narrow state subscriptions
- Add 14 unit tests covering store initialization, slice behaviors, and batcher timing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/renderer/state/slices/communication.ts

@@ -0,0 +1,17 @@
+import type { StateCreator } from "zustand";
+import type { AppState } from "../store";
+
+export interface CommunicationSlice {
+  // Placeholder for future message state -- this slice will be populated
+  // during component decomposition. The communication component currently
+  // manages its own internal state.
+}
+
+export const createCommunicationSlice: StateCreator<
+  AppState,
+  [["zustand/immer", never]],
+  [],
+  CommunicationSlice
+> = () => ({
+  // Empty state for now
+});