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/ipc.ts

@@ -16,6 +16,12 @@ import {
 
 export const IPC_CHANNEL = 'trpc';
 
+/** Context passed to every tRPC procedure via the IPC bridge. */
+export type TRPCContext = {
+  /** The IPC sender — available for streaming chunks back to the renderer. */
+  sender?: Electron.WebContents;
+};
+
 interface IPCRequest {
   method: 'request';
   operation: {
@@ -57,7 +63,7 @@ export function createIPCHandler<TRouter extends AnyRouter>({
         router,
         path,
         getRawInput: async () => rawInput,
-        ctx: {},
+        ctx: { sender: event.sender } satisfies TRPCContext,
         type,
         signal: undefined as unknown as AbortSignal,
         batchIndex: 0,