task(A4.2): migrate rect tool to v2 plugin

frontend/tests/pilotTools.test.ts

@@ -80,6 +80,46 @@ describe('A3 pilot: line tool', () => {
   });
 });
 
+describe('A4.2 pilot: rect tool', () => {
+  it('erzeugt Rechteck mit BBox-Konvention; ein undo entfernt es', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const rect = coreDrawingPlugin.tools?.find((t) => t.manifest.id === 'rect');
+    expect(rect).toBeDefined();
+
+    rect!.handlers.down!(pe(10, 10), ctx);
+    rect!.handlers.move!(pe(110, 60), ctx);
+    expect(ctx.previews.length).toBe(1);       // Live-Vorschau
+    rect!.handlers.up!(pe(110, 60), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('rect');
+    // Legacy-BBox-Konvention: Zentrum zwischen beiden Ecken
+    expect(all[0].x).toBe(60);
+    expect(all[0].y).toBe(35);
+    expect(all[0].width).toBe(100);
+    expect(all[0].height).toBe(50);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('cancel verwirft das laufende Rechteck', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const rect = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'rect')!;
+
+    rect.handlers.down!(pe(5, 5), ctx);
+    rect.handlers.cancel!(ctx);
+    rect.handlers.up!(pe(50, 50), ctx);
+
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
 describe('A3 pilot: select tool', () => {
   function makeBridge(elements: CADElement[]) {
     let ids: string[] = [];