feat: 形状工具改为拖拽创建，五种形状 + Shift 约束比例（T12）

src/components/Workspace.vue

@@ -4,6 +4,7 @@ import { useEditor } from "@/editor/useEditor";
 import { useViewport } from "@/editor/useViewport";
 import { initHistory, commit } from "@/editor/useHistory";
 import { openContextMenu } from "@/editor/useContextMenu";
+import { attachShapeTool } from "@/editor/useShapeTool";
 
 /**
  * 画布区。**画布元素的像素尺寸跟着容器走**（它是「视口」），
@@ -16,7 +17,7 @@ import { openContextMenu } from "@/editor/useContextMenu";
  *
  * **这个文件由主控独占。**
  */
-const { mount, unmount, getCanvas, tool, addText, addRect } = useEditor();
+const { mount, unmount, getCanvas, tool, addText } = useEditor();
 const { zoomAt, panBy, zoomToFit } = useViewport();
 
 const canvasEl = ref<HTMLCanvasElement | null>(null);
@@ -26,6 +27,7 @@ let spaceDown = false;
 let panning = false;
 let lastX = 0;
 let lastY = 0;
+let detachShapeTool: (() => void) | null = null;
 
 /**
  * 视口尺寸跟着容器走。
@@ -86,14 +88,12 @@ function onPointerDown(e: PointerEvent) {
     (e.currentTarget as HTMLElement).setPointerCapture(e.pointerId);
     return;
   }
+  // 形状工具：拖拽创建由 useShapeTool 的 attachShapeTool 接管，这里完全让开。
+  if (e.button === 0 && tool.value === "shape") return;
+
   // 非选择工具：在点击处放一个新对象，然后回到选择工具（和 Figma 一致）
   if (e.button === 0 && tool.value !== "select") {
-    const c = getCanvas();
-    const p = c.getViewportPoint(e);
-    const scene = c.getScenePoint(e);
-    void p;
     if (tool.value === "text") addText();
-    else if (tool.value === "shape") addRect({ x: scene.x, y: scene.y });
     if (tool.value !== "background") {
       tool.value = "select";
       commit();
@@ -126,6 +126,8 @@ onMounted(() => {
   // 尺寸与首次适应交给 resize()，它会等到 stage 真的有尺寸了再做。
   resize();
   initHistory();
+  // 形状工具的指针交互单独挂在画布上，这里只负责装/卸。
+  detachShapeTool = attachShapeTool(c);
   // 拖拽 / 缩放 / 旋转结束都算一步操作。
   c.on("object:modified", () => commit());
   observer = new ResizeObserver(resize);
@@ -136,6 +138,7 @@ onMounted(() => {
 
 onBeforeUnmount(() => {
   observer?.disconnect();
+  detachShapeTool?.();
   window.removeEventListener("keydown", onKeyDown);
   window.removeEventListener("keyup", onKeyUp);
   unmount();