feat: Integrate GitHub Copilot SDK and LangChain for provider-independent orchestration

- Added @github/copilot-sdk and related dependencies for GitHub Copilot integration.
- Implemented ChatCopilot adapter for LangChain compatibility.
- Created LLM factory to return provider-specific models (OpenAI, Anthropic, Copilot).
- Developed Orchestrator agent using LangGraph for intent routing and context assembly.
- Enhanced IPC communication for streaming AI responses to the renderer.
- Updated progress documentation with implementation details and learnings.

src/main/router/index.ts

@@ -6,8 +6,10 @@ import { getDb } from '../db';
 import { clients, projects, tasks, checkpoints, notes, taskComments } from '../db/schema';
 import { getStore } from '../store';
 import { saveTokenAndInit, hasActiveToken } from '../ai/provider';
+import { orchestrate } from '../ai/orchestrator';
+import type { TRPCContext } from '../ipc';
 
-const t = initTRPC.create();
+const t = initTRPC.context<TRPCContext>().create();
 
 const router = t.router;
 const publicProcedure = t.procedure;
@@ -492,7 +494,18 @@ const aiRouter = router({
         projectId: z.string().optional(),
       }),
     }))
-    .mutation(() => ({ response: '' })),
+    .mutation(async ({ input, ctx }) => {
+      try {
+        return await orchestrate({
+          message: input.message,
+          context: input.context,
+          sender: ctx.sender,
+        });
+      } catch (err) {
+        const msg = err instanceof Error ? err.message : 'Unknown error';
+        return { response: '', error: msg };
+      }
+    }),
   setToken: publicProcedure
     .input(z.object({ token: z.string() }))
     .mutation(async ({ input }) => {