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/server/src/server/messages.ts

@@ -450,6 +450,7 @@ export const AgentPermissionResponseMessageSchema = z.object({
 export const GitDiffRequestSchema = z.object({
   type: z.literal("git_diff_request"),
   agentId: z.string(),
+  requestId: z.string().optional(),
 });
 
 const FileExplorerEntrySchema = z.object({
@@ -736,6 +737,7 @@ export const GitDiffResponseSchema = z.object({
     agentId: z.string(),
     diff: z.string(),
     error: z.string().nullable(),
+    requestId: z.string().optional(),
   }),
 });
 

packages/server/src/server/session.ts

@@ -840,7 +840,7 @@ export class Session {
           break;
 
         case "git_diff_request":
-          await this.handleGitDiffRequest(msg.agentId);
+          await this.handleGitDiffRequest(msg.agentId, msg.requestId);
           break;
 
         case "file_explorer_request":
@@ -1967,7 +1967,7 @@ export class Session {
   /**
    * Handle git diff request for an agent
    */
-  private async handleGitDiffRequest(agentId: string): Promise<void> {
+  private async handleGitDiffRequest(agentId: string, requestId?: string): Promise<void> {
     console.log(
       `[Session ${this.clientId}] Handling git diff request for agent ${agentId}`
     );
@@ -1983,6 +1983,7 @@ export class Session {
             agentId,
             diff: "",
             error: `Agent not found: ${agentId}`,
+            requestId,
           },
         });
         return;
@@ -1998,6 +1999,7 @@ export class Session {
           agentId,
           diff: stdout,
           error: null,
+          requestId,
         },
       });
 
@@ -2015,6 +2017,7 @@ export class Session {
           agentId,
           diff: "",
           error: error.message,
+          requestId,
         },
       });
     }