feat(git-diff): add React Query with pull-to-refresh and cleaner diff display

- Add useGitDiffQuery hook using React Query for caching and revalidation
- Add sendRpcRequest utility for promisified WebSocket RPC with requestId matching
- Add requestId to git_diff_request/response for proper request correlation
- Enable pull-to-refresh via RefreshControl in GitDiffPane
- Auto-revalidate when sidebar opens with "changes" tab active
- Clean up diff display: remove metadata noise, strip +/- prefixes
- Default both sidebars open on web platform

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/app/src/stores/explorer-sidebar-store.ts

@@ -1,6 +1,7 @@
 import { create } from "zustand";
 import { persist, createJSONStorage } from "zustand/middleware";
 import AsyncStorage from "@react-native-async-storage/async-storage";
+import { Platform } from "react-native";
 
 type ExplorerTab = "changes" | "files";
 export type ViewMode = "list" | "grid";
@@ -10,6 +11,8 @@ export const DEFAULT_EXPLORER_SIDEBAR_WIDTH = 400;
 export const MIN_EXPLORER_SIDEBAR_WIDTH = 280;
 export const MAX_EXPLORER_SIDEBAR_WIDTH = 800;
 
+const DEFAULT_OPEN = Platform.OS === "web";
+
 interface ExplorerSidebarState {
   isOpen: boolean;
   activeTab: ExplorerTab;
@@ -32,7 +35,7 @@ function clampWidth(width: number): number {
 export const useExplorerSidebarStore = create<ExplorerSidebarState>()(
   persist(
     (set) => ({
-      isOpen: false,
+      isOpen: DEFAULT_OPEN,
       activeTab: "changes",
       width: DEFAULT_EXPLORER_SIDEBAR_WIDTH,
       viewMode: "list",

packages/app/src/stores/sidebar-store.ts

@@ -1,6 +1,7 @@
 import { create } from "zustand";
 import { persist, createJSONStorage } from "zustand/middleware";
 import AsyncStorage from "@react-native-async-storage/async-storage";
+import { Platform } from "react-native";
 
 interface SidebarState {
   isOpen: boolean;
@@ -9,10 +10,12 @@ interface SidebarState {
   close: () => void;
 }
 
+const DEFAULT_OPEN = Platform.OS === "web";
+
 export const useSidebarStore = create<SidebarState>()(
   persist(
     (set) => ({
-      isOpen: false,
+      isOpen: DEFAULT_OPEN,
       toggle: () => set((state) => ({ isOpen: !state.isOpen })),
       open: () => set({ isOpen: true }),
       close: () => set({ isOpen: false }),