fix: v2.1 3D 渲染问题根治(profileGeo 自交破面+扇矩形 NaN)

- profileGeo 外轮廓路径自相交(闭合斜边穿过槽口)导致三角剖分破面
  重写为正确顶点顺序的 U 槽简单多边形
- 型材截面挤出抽为共享模块 three/profileGeo.ts(+geometryIsValid 校验器)
- inferSashGlyphs 兜底 bboxOf 误传段对象→修正为有限值点集
  (修复扇矩形 NaN 序列化为 null 的问题)
- 新增 scripts/validate3d.cjs: 254 样板×3700 网格×798 扇
  逐网格 NaN 检测全部通过; 窄条扇合法跳过

frontend/src/components/WindoorThreed.vue

@@ -56,6 +56,7 @@ import {
   bboxOf, inferSashGlyphs, parseDrawing, regionPoints, replayShape,
   type DrawingData, type Pt,
 } from '../types/drawing'
+import { profileGeo } from '../three/profileGeo'
 
 interface BBox { x0: number; y0: number; x1: number; y1: number }
 
@@ -110,42 +111,6 @@ function overlapArea(a: BBox, b: BBox): number {
 }
 
 /** 型材截面: 多腔体 + 玻璃槽(比例依据真实 DXF 截面学习: 深度46-90/面宽65-130/腔体3-6/壁厚≈深度1/30) */
-function profileGeo(len: number, fw: number, depth: number, chambers: number): THREE.BufferGeometry {
-  const t = Math.max(0.004, depth * 0.14)          // 壁厚
-  const g = Math.max(0.006, depth * 0.2)           // 玻璃槽深
-  const s = new THREE.Shape()
-  // 外轮廓: u=0 侧开玻璃槽
-  s.moveTo(0, t)
-  s.lineTo(g, t)
-  s.lineTo(g, fw - t)
-  s.lineTo(0, fw - t)
-  s.lineTo(0, 0)
-  s.lineTo(depth, 0)
-  s.lineTo(depth, fw)
-  s.lineTo(g, fw)
-  s.closePath()
-  // 腔体孔洞(隔热/加强腔)
-  const cH = fw - t * 2
-  const usable = depth - g - t * (chambers + 1)
-  const cw = usable / chambers
-  if (cw > t) {
-    for (let i = 0; i < chambers; i++) {
-      const hx = g + t + i * (cw + t)
-      const hole = new THREE.Path()
-      hole.moveTo(hx, t)
-      hole.lineTo(hx + cw, t)
-      hole.lineTo(hx + cw, t + cH)
-      hole.lineTo(hx, t + cH)
-      hole.closePath()
-      s.holes.push(hole)
-    }
-  }
-  const geo = new THREE.ExtrudeGeometry(s, { depth: len, bevelEnabled: false })
-  geo.translate(0, 0, -len / 2)
-  return geo
-}
-
-/** 沿 X 轴的型材杆(槽口朝 -Z 玻璃面) */
 function barX(parent: THREE.Group, mat: THREE.Material, len: number, fw: number,
               depth: number, cx: number, cy: number, cz: number, chambers = 2) {
   const geo = profileGeo(len, fw, depth, chambers)