feat(v2): add frontend remote machine integration

remote-bridge.ts adapter for machine management IPC. machines.svelte.ts
store for remote machine state. Layout store extended with
remoteMachineId on Pane interface. agent-bridge.ts and pty-bridge.ts
route to remote commands when remoteMachineId is set. SettingsDialog
gains Remote Machines section. Sidebar auto-groups remote panes by
machine label.

v2/src/lib/stores/machines.svelte.ts

@@ -0,0 +1,97 @@
+// Remote machines store — tracks connection state for multi-machine support
+
+import {
+  listRemoteMachines,
+  addRemoteMachine,
+  removeRemoteMachine,
+  connectRemoteMachine,
+  disconnectRemoteMachine,
+  onRemoteMachineReady,
+  onRemoteMachineDisconnected,
+  onRemoteError,
+  type RemoteMachineConfig,
+  type RemoteMachineInfo,
+} from '../adapters/remote-bridge';
+import { notify } from './notifications.svelte';
+
+export interface Machine extends RemoteMachineInfo {}
+
+let machines = $state<Machine[]>([]);
+
+export function getMachines(): Machine[] {
+  return machines;
+}
+
+export function getMachine(id: string): Machine | undefined {
+  return machines.find(m => m.id === id);
+}
+
+export async function loadMachines(): Promise<void> {
+  try {
+    machines = await listRemoteMachines();
+  } catch (e) {
+    console.warn('Failed to load remote machines:', e);
+  }
+}
+
+export async function addMachine(config: RemoteMachineConfig): Promise<string> {
+  const id = await addRemoteMachine(config);
+  machines.push({
+    id,
+    label: config.label,
+    url: config.url,
+    status: 'disconnected',
+    auto_connect: config.auto_connect,
+  });
+  return id;
+}
+
+export async function removeMachine(id: string): Promise<void> {
+  await removeRemoteMachine(id);
+  machines = machines.filter(m => m.id !== id);
+}
+
+export async function connectMachine(id: string): Promise<void> {
+  const machine = machines.find(m => m.id === id);
+  if (machine) machine.status = 'connecting';
+  try {
+    await connectRemoteMachine(id);
+    if (machine) machine.status = 'connected';
+  } catch (e) {
+    if (machine) machine.status = 'error';
+    throw e;
+  }
+}
+
+export async function disconnectMachine(id: string): Promise<void> {
+  await disconnectRemoteMachine(id);
+  const machine = machines.find(m => m.id === id);
+  if (machine) machine.status = 'disconnected';
+}
+
+// Initialize event listeners for machine status updates
+export async function initMachineListeners(): Promise<void> {
+  await onRemoteMachineReady((msg) => {
+    const machine = machines.find(m => m.id === msg.machineId);
+    if (machine) {
+      machine.status = 'connected';
+      notify('success', `Connected to ${machine.label}`);
+    }
+  });
+
+  await onRemoteMachineDisconnected((msg) => {
+    const machine = machines.find(m => m.id === msg.machineId);
+    if (machine) {
+      machine.status = 'disconnected';
+      notify('warning', `Disconnected from ${machine.label}`);
+    }
+  });
+
+  await onRemoteError((msg) => {
+    const machine = machines.find(m => m.id === msg.machineId);
+    if (machine) {
+      machine.status = 'error';
+      notify('error', `Error from ${machine.label}: ${msg.error}`);
+    }
+  });
+}