feat(FN-3507): block dispatch when project lacks node mapping

Adds validation to block task dispatch when no project-node mapping exists (FN-3507), including a read helper in CentralCore and a new `node-dispatch-validation` module integrated into the scheduler and in-process runtime, with test coverage across routing and validation scenarios.

Fusion-Task-Id: FN-3507

packages/core/src/central-core.ts

@@ -1769,6 +1769,16 @@ export class CentralCore extends EventEmitter<CentralCoreEvents> {
     return row ? this.rowToProjectNodePathMapping(row) : undefined;
   }
 
+  async getProjectNodePath(projectId: string, nodeId: string): Promise<string | undefined> {
+    this.ensureInitialized();
+
+    const row = this.db!
+      .prepare("SELECT path FROM projectNodePathMappings WHERE projectId = ? AND nodeId = ?")
+      .get(projectId, nodeId) as { path: string } | undefined;
+
+    return row?.path;
+  }
+
   async listProjectNodePathMappings(filters?: {
     projectId?: string;
     nodeId?: string;