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/contracts/channels.ts

@@ -26,6 +26,7 @@ export const ipcChannels = {
   sendSessionMessage: 'sessions:send-message',
   cancelSessionTurn: 'sessions:cancel-turn',
   resolveSessionApproval: 'sessions:resolve-approval',
+  resolveSessionUserInput: 'sessions:resolve-user-input',
   querySessions: 'sessions:query',
   updateSessionModelConfig: 'sessions:update-model-config',
   selectProject: 'selection:project',