fix: 推拉滑扇附着上半区(对齐 31729 实况)

- 共享推断模块 inferSashGlyphs: DoubleSash 滑扇对附着较高的重放区域
  (不依赖 vendor polyId 序, 消除推拉窗滑扇落下半区的错位)
- 31729 行为验证: 滑扇矩形 y 2225.8-3370.8 = 上半区 ✓
- verify 脚本 console 过滤放宽([C 前缀统一捕获)

frontend/src/types/drawing.ts

@@ -269,7 +269,12 @@ export function inferSashGlyphs(shape: FrameShape, replayed?: Segment[][]): {
     const rect = sub.bd ? bdRect(sub.bd) : null
     if (rect) { pushGlyphs(rect, entries, sub); continue }
     const idx = sub.polyId?.idx
-    const rb = idx != null && regionBBs[idx] ? regionBBs[idx] : null
+    let rb = idx != null && regionBBs[idx] ? regionBBs[idx] : null
+    // 推拉双扇: 附着较高的区域(推拉窗滑扇在上半部, 对齐 31729 实况)
+    const kind = sub.type === 'DoubleSash' ? 'sliding' : 'casement'
+    if (kind === 'sliding') {
+      rb = regionBBs.reduce((p, c) => (!p || (c.y0 + c.y1) / 2 > (p.y0 + p.y1) / 2 ? c : p), null as BBox | null)
+    }
     if (rb) {
       if (entries.length === 2) {
         const w = rb.x1 - rb.x0, h = rb.y1 - rb.y0