lazy backend boot and rename workspace to project

Backend isolate now boots in two phases: resolve toolchain on spawn
(binary availability only), initialize services on project.open. The
dispatcher stays empty until a project activates — IPC requests before
that return "No project active".

Scheduler ticker only runs while a project is open. Fires an immediate
first cycle on ProjectOpened so sidebar panels refresh without waiting
for the next interval. Stops on ProjectClosed.

Renamed workspace → project throughout backend messages
(project.validate, project.open, project.ready), callbacks
(onProjectOpen, onValidateProject), and methods
(openProject, validateProject, resolveProject).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/src/daemon/dispatcher.dart

@@ -16,6 +16,13 @@ class DaemonDispatcher {
     _handlers[cmd] = handler;
   }
 
+  /// Remove all registered handlers except ping/version.
+  void clear() {
+    _handlers.removeWhere((k, _) => k != 'ping' && k != 'version');
+  }
+
+  bool get isEmpty => _handlers.length <= 2; // only ping + version
+
   Future<IpcResponse> dispatch(IpcRequest req) async {
     final h = _handlers[req.cmd];
     if (h == null) {