feat(v2): refactor reconnection probe to TCP-only and add frontend listeners

Replace attempt_ws_connect() with attempt_tcp_probe() in RemoteManager to
avoid allocating per-connection resources (PtyManager, SidecarManager) on
the relay during reconnection probes. Add onRemoteMachineReconnecting and
onRemoteMachineReconnectReady event listeners in remote-bridge.ts. Wire
machines store to auto-reconnect when relay becomes reachable.

v2/src/lib/adapters/remote-bridge.ts

@@ -120,3 +120,24 @@ export async function onRemoteError(
     callback(event.payload);
   });
 }
+
+export interface RemoteReconnectingEvent {
+  machineId: string;
+  backoffSecs: number;
+}
+
+export async function onRemoteMachineReconnecting(
+  callback: (msg: RemoteReconnectingEvent) => void,
+): Promise<UnlistenFn> {
+  return listen<RemoteReconnectingEvent>('remote-machine-reconnecting', (event) => {
+    callback(event.payload);
+  });
+}
+
+export async function onRemoteMachineReconnectReady(
+  callback: (msg: RemoteMachineEvent) => void,
+): Promise<UnlistenFn> {
+  return listen<RemoteMachineEvent>('remote-machine-reconnect-ready', (event) => {
+    callback(event.payload);
+  });
+}