feat(editor): 机位画幅遮幅与监视器全屏对齐

主视口机位视角按传感器画幅加 letterbox 遮幅，使主视口、镜头监视器与视频导出的取景逐像素同源，虚化按传感器画幅归一化。镜头监视器新增全屏查看（Esc 关闭），支持拖拽瞄准与单击对焦并显示景深诊断读数，像素比上限改为 2 以消除机位视角的放大模糊。监视器与主视口统一按自动切机位口径解析当前机位。相机面板新增所选物体距离显示与一键对焦。

src/editor/panels/CameraPanel.test.tsx

@@ -125,6 +125,24 @@ it("uses the provided right inspector layout for camera properties", () => {
   expect(fovField).toBeInTheDocument();
 });
 
+it("shows the selected subject distance and focuses the camera onto it in one click", async () => {
+  const user = userEvent.setup();
+  // 选中可对焦物体（角色）后，面板直接给出「机位 → 物体」的实测距离
+  useDirectorStore.setState({
+    ...useDirectorStore.getState(),
+    selectedObjectId: "char_default_a",
+  });
+  render(<CameraPanel />);
+
+  // 默认机位 [0, 1.55, 5.4] → 角色焦点 [0, 0.99, 0] ≈ 5.4m
+  expect(screen.getByLabelText("所选物体距离")).toHaveTextContent("所选物体 5.4 m");
+
+  await user.click(screen.getByRole("button", { name: "对焦到所选物体" }));
+
+  const camera = useDirectorStore.getState().project.cameras[0];
+  expect(camera.focusDistance).toBeCloseTo(5.43, 1);
+});
+
 it("keeps camera panel tab labels in fixed slots while switching tabs", async () => {
   const user = userEvent.setup();
   const { container } = render(<CameraPanel />);