fix(dashboard): start engine for every registered project on first access

Tasks in projects other than the primary (cwd) project were never triaged
because only one ProjectEngine was started. When a project is accessed via
?projectId= API/SSE, getOrCreateProjectStore created a TaskStore but left
the Scheduler, TriageProcessor, and TaskExecutor unstarted.

Fix: introduce setOnProjectFirstCreated callback in project-store-resolver
so the dashboard server is notified when any new project is first accessed.
dashboard.ts creates a ProjectManager that lazily starts an InProcessRuntime
(Scheduler + TriageProcessor + TaskExecutor) for each project the first time
it is accessed — works for any number of registered projects.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/dashboard/src/project-store-resolver.ts

@@ -37,6 +37,21 @@ const pendingCreations = new Map<string, Promise<TaskStore>>();
  */
 const initializedProjects = new Set<string>();
 
+/**
+ * Optional callback invoked once when a new project store is first created.
+ * Used by the dashboard server to lazily start an engine for secondary projects.
+ */
+let _onProjectFirstCreated: ((projectId: string) => void) | undefined;
+
+/**
+ * Register a callback to be called once when a new project is first accessed.
+ * The callback fires after the store is cached — exactly once per projectId.
+ * Pass `undefined` to clear the callback.
+ */
+export function setOnProjectFirstCreated(cb: ((projectId: string) => void) | undefined): void {
+  _onProjectFirstCreated = cb;
+}
+
 /**
  * Get or create a cached TaskStore for the given projectId.
  *
@@ -81,6 +96,12 @@ export async function getOrCreateProjectStore(projectId: string): Promise<TaskSt
 
     storeCache.set(projectId, store);
     pendingCreations.delete(projectId);
+
+    // Notify once that a new project was first accessed
+    if (_onProjectFirstCreated) {
+      _onProjectFirstCreated(projectId);
+    }
+
     return store;
   })();