feat: add MCP OAuth authentication frontend wiring and banner

- Add McpOauthRequiredEvent and McpOauthStaticClientConfigEvent to sidecar contracts
- Add PendingMcpAuthRecord domain type with status tracking (pending/authenticating/failed/done)
- Add pendingMcpAuth field to SessionRecord for session-level auth state
- Wire onMcpOAuthRequired callback through sidecarProcess, runTurnPending, and AryxAppService
- Handle mcp-oauth-required events: set session pendingMcpAuth, clear on turn finalize/cancel
- Add dismissSessionMcpAuth IPC channel with preload binding and handler registration
- Create McpAuthBanner component (amber-themed, shows server name/URL, dismiss button)
- Integrate McpAuthBanner into ChatPane with placeholder text and App.tsx callback
- Update test fixtures for new RunTurnPendingCommand.onMcpOAuthRequired field

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

src/preload/index.ts

@@ -39,6 +39,7 @@ const api: ElectronApi = {
   resolveSessionUserInput: (input) => ipcRenderer.invoke(ipcChannels.resolveSessionUserInput, input),
   setSessionInteractionMode: (input) => ipcRenderer.invoke(ipcChannels.setSessionInteractionMode, input),
   dismissSessionPlanReview: (input) => ipcRenderer.invoke(ipcChannels.dismissSessionPlanReview, input),
+  dismissSessionMcpAuth: (input) => ipcRenderer.invoke(ipcChannels.dismissSessionMcpAuth, input),
   updateSessionModelConfig: (input) =>
     ipcRenderer.invoke(ipcChannels.updateSessionModelConfig, input),
   querySessions: (input) => ipcRenderer.invoke(ipcChannels.querySessions, input),