feat(FN-2855): route scheduled tasks using effective node resolution

- Add an effective node resolver with task override, project default, and local fallback precedence.
- Wire scheduler dispatch to persist effectiveNodeId/effectiveNodeSource and log resolved node routing.
- Add coverage for effective node resolution and scheduler node routing integration behavior.
- Stabilize workspace test resolution by adding @fusion/core and @fusion/plugin-sdk aliases across Vitest configs.

packages/engine/src/__tests__/scheduler.test.ts

@@ -818,6 +818,8 @@ describe("Scheduler", () => {
         blockedBy: null,
         baseBranch: undefined,
         worktree: "/test/project/.worktrees/fn-010",
+        effectiveNodeId: null,
+        effectiveNodeSource: "local",
       });
       expect(moveTask).toHaveBeenCalledWith("FN-010", "in-progress");
       expect(updateTask.mock.invocationCallOrder[0]).toBeLessThan(moveTask.mock.invocationCallOrder[0]);
@@ -854,12 +856,16 @@ describe("Scheduler", () => {
         blockedBy: null,
         baseBranch: undefined,
         worktree: "/test/project/.worktrees/amber-aspen",
+        effectiveNodeId: null,
+        effectiveNodeSource: "local",
       });
       expect(updateTask).toHaveBeenNthCalledWith(2, "FN-012", {
         status: null,
         blockedBy: null,
         baseBranch: undefined,
         worktree: "/test/project/.worktrees/amber-aspen-2",
+        effectiveNodeId: null,
+        effectiveNodeSource: "local",
       });
 
       randomSpy.mockRestore();