feat(FN-2519): add remote tunnel manager for settings sync

- Add remote-access contracts, provider adapters, and a tunnel process manager with lifecycle handling
- Wire tunnel manager into ProjectEngine startup/shutdown flow and export new remote-access modules
- Update settings modal UX for remote auth URLs, including wrapping and related UI test coverage
- Document tunnel manager behavior and remote settings sync details in architecture, CLI, and settings docs

packages/engine/src/logger.ts

@@ -104,6 +104,9 @@ export const heartbeatLog = createLogger("heartbeat");
 /** Logger for remote node runtime/client subsystems. */
 export const remoteNodeLog = createLogger("remote-node");
 
+/** Logger for remote tunnel process orchestration subsystem. */
+export const remoteTunnelLog = createLogger("remote-tunnel");
+
 /** Logger for periodic node health monitor subsystem. */
 export const nodeHealthMonitorLog = createLogger("node-health-monitor");