fix(POSTV1-editor): 修复多选拖动与底图调整

tests/unit/wp4-02-editor-elements.test.ts

@@ -73,6 +73,10 @@ describe("TDD-WP4-CAN-001 canvas selection and limit", () => {
       identity(1).elementId,
       identity(2).elementId,
     ]);
+    expect(controller.selectAt({ x: 0.2, y: 0.2 }, { append: true, preserveSelection: true })).toEqual([
+      identity(1).elementId,
+      identity(2).elementId,
+    ]);
   });
 });
 
@@ -97,6 +101,19 @@ describe("TDD-WP4-STK-001 sticker transformations", () => {
     });
   });
 
+  it("uses one bounded delta for distant selected elements", () => {
+    const controller = new CanvasElementController(state([
+      sticker(1, { position: { x: 0.1, y: 0.2 } }),
+      sticker(2, { position: { x: 0.9, y: 0.8 } }),
+    ]));
+    controller.selectIds([identity(1).elementId, identity(2).elementId]);
+    controller.moveSelected({ x: 0.2, y: 0.3 }, { snap: false });
+    expect(controller.value.elements.map(({ position }) => position)).toEqual([
+      { x: 0.2, y: 0.4 },
+      { x: 1, y: 1 },
+    ]);
+  });
+
   it("duplicates, reorders and deletes selected stickers while preserving stable resource identity", () => {
     const controller = new CanvasElementController(state([sticker(1), sticker(2, { position: { x: 0.7, y: 0.7 } })]));
     controller.selectById(identity(1).elementId);