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/engine/src/__tests__/node-dispatch-validation.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, it } from "vitest";
+import { validateProjectNodeMapping } from "../node-dispatch-validation.js";
+
+describe("validateProjectNodeMapping", () => {
+  it("allows dispatch when mapping path is present", () => {
+    expect(
+      validateProjectNodeMapping({ nodeId: "node-1", mappedPath: "/work/project" }),
+    ).toEqual({ allowed: true });
+  });
+
+  it("blocks dispatch when mapping is missing or blank", () => {
+    expect(
+      validateProjectNodeMapping({ nodeId: "node-1", mappedPath: undefined }),
+    ).toEqual({
+      allowed: false,
+      code: "missing-project-mapping",
+      reason: "Execution blocked: project has no path mapping for node node-1",
+    });
+
+    expect(
+      validateProjectNodeMapping({ nodeId: "node-1", mappedPath: "   " }),
+    ).toEqual({
+      allowed: false,
+      code: "missing-project-mapping",
+      reason: "Execution blocked: project has no path mapping for node node-1",
+    });
+  });
+});