test: stub readNodeRect in the ghost placement layout mock

The hand-rolled layoutStore mock predates this branch's store-backed
geometry reads, so every ghost test threw on `LGraphNode.boundingRect`.
Mirrors the stub already added to the slot hit-detection mock.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: DrJKL

src/lib/litegraph/src/LGraphCanvas.ghost.test.ts

@@ -14,6 +14,7 @@ vi.mock('@/renderer/core/layout/store/layoutStore', () => ({
     querySlotAtPoint: vi.fn(),
     queryRerouteAtPoint: vi.fn(),
     getNodeLayoutRef: vi.fn(() => ({ value: null })),
+    readNodeRect: vi.fn(() => false),
     getSlotLayout: vi.fn(),
     setSource: vi.fn(),
     setActor: vi.fn()