fix: v2.2 修复 3D 截图纯色空白(墙体尺寸单位错误)

- 根因: 墙体宽度 bw=1/S*0.72 误用模型单位(≈最大边长*0.72, 数千单位)
  而放置坐标是世界单位(窗体≈1), 相机被包在巨墙内只见背景色
- 改为世界单位: 上下墙覆盖窗洞±2.2x0.55, 左右墙 0.55x窗高
- 墙体不投影(避免自遮挡), 地面尺寸同步修正
- Node 验证四墙尺寸全部 ≤2.2 世界单位

frontend/src/components/WindoorThreed.vue

@@ -308,30 +308,34 @@ function build(drawing: DrawingData) {
     }
   }
 
-  // ---- 墙体洞口 + 地面 ----
+  // ---- 墙体洞口 + 地面（世界单位：窗体约 1 单位见方）----
   if (showWall.value) {
-    const bw = 1 / S * 0.72, bh = 1 / S * 0.72
-    const wx0 = -gw * S / 2 - 0.06, wx1 = gw * S / 2 + 0.06
-    const wy0 = -gh * S / 2 - 0.04, wy1 = gh * S / 2 + 0.06
+    const hw = gw * S / 2 + 0.05           // 窗洞半宽
+    const hh = gh * S / 2 + 0.05           // 窗洞半高
+    const side = 0.55                       // 上下墙高度/左右墙宽度
     const wt = DEPTH * 3
     const wallBoxes: [number, number, number, number, number][] = [
-      [wx0 - bw, wy1, bw * 2, bh],                    // 上
-      [wx0 - bw, wy0 - bh, bw * 2, bh],               // 下
-      [wx0 - bw, wy0, bw, wy1 - wy0],                 // 左
-      [wx1, wy0, bw, wy1 - wy0],                      // 右
+      [-hw - side, hh, side * 2 + hw * 2, side],   // 上
+      [-hw - side, -hh - side, side * 2 + hw * 2, side], // 下
+      [-hw - side, -hh, side, hh * 2],             // 左
+      [hw, -hh, side, hh * 2],                     // 右
     ]
     for (const [px, py, pw, ph] of wallBoxes) {
       const m = new THREE.Mesh(new THREE.BoxGeometry(pw, ph, wt), wallMat)
       m.position.set(px + pw / 2, py + ph / 2, 0)
       m.receiveShadow = true
+      m.userData.isWall = true
       sceneRoot.add(m)
     }
-    const ground = new THREE.Mesh(new THREE.BoxGeometry(bw * 4, 0.02, DEPTH * 8), groundMat)
-    ground.position.set(0, wy0 - 0.02, DEPTH * 2)
+    const ground = new THREE.Mesh(new THREE.BoxGeometry(3, 0.02, DEPTH * 8), groundMat)
+    ground.position.set(0, -hh - side - 0.02, DEPTH * 2)
     ground.receiveShadow = true
     sceneRoot.add(ground)
   }
-  sceneRoot.traverse(o => { if ((o as THREE.Mesh).isMesh) { o.castShadow = true; o.receiveShadow = true } })
+  sceneRoot.traverse(o => {
+    const m = o as THREE.Mesh
+    if (m.isMesh) { m.castShadow = !m.userData.isWall; m.receiveShadow = true }
+  })
   // 玻璃不投影
   sceneRoot.traverse(o => {
     const mat = (o as THREE.Mesh).material as THREE.Material | undefined