feat: add ask_user interactive user input to frontend

Wire the sidecar user-input-requested protocol event through the main
process, IPC layer, and renderer UI so agents can ask the user
interactive questions with choices and freeform input.

- Add UserInputRequestedEvent and ResolveUserInputCommand to sidecar
  protocol types
- Add resolveUserInput method to SidecarClient and onUserInput callback
  to runTurn
- Create PendingUserInputRecord domain type and add pendingUserInput to
  SessionRecord
- Add handleUserInputRequested and resolveSessionUserInput to
  AryxAppService with handle management
- Register sessions:resolve-user-input IPC channel with preload bridge
- Create UserInputBanner component with choice buttons and freeform
  input
- Integrate UserInputBanner into ChatPane with header indicator

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/shared/domain/userInput.ts

@@ -0,0 +1,14 @@
+export type UserInputStatus = 'pending' | 'answered';
+
+export interface PendingUserInputRecord {
+  id: string;
+  status: UserInputStatus;
+  agentId?: string;
+  agentName?: string;
+  question: string;
+  choices?: string[];
+  allowFreeform: boolean;
+  requestedAt: string;
+  answer?: string;
+  answeredAt?: string;
+}