feat(viewer2d): render DWG lineweight in screen pixels

Every line was drawn 1px regardless of its CAD lineweight. Two causes:
the dwg-wasm parseResult never carried the field (acadrust reads
EntityCommon::line_weight but it was dropped in serialization), and the
renderer merged all segments into one LineSegments whose
LineBasicMaterial.linewidth WebGL ignores.

Resolve ByLayer/ByBlock/Default per entity and bucket segments by
dash|lineweight. Weighted buckets get their own LineSegments2 +
LineMaterial with worldUnits:false, so width stays constant in pixels
while zooming - AutoCAD LWDISPLAY semantics - at 8 px/mm (0.25mm = 2px).
Anything at or below the 0.25mm default stays in the hairline batch so
drawings that never assigned a weight render exactly as before.

Fat batches are instanced, so layer masking compacts the instance buffer
and lowers instanceCount instead of rewriting an index; slotOf tracks
where each segment moved so the selection highlight still finds its
vertices. Per-entity color spans (meta.spans) let the highlight repaint
across the hairline batch and every bucket it touched. Buckets past
400k segments fall back to hairline to bound GPU/heap cost.

Display follows the drawing's LWDISPLAY and can be forced from the
toolbar; the property panel now shows the entity lineweight.

Verified headless at a fixed camera on the 65k-entity road drawing:
cyan road edge 2px -> 5px, layer hide/restore returns the exact baseline
pixel counts, and a 0.35mm LWPOLYLINE selects and highlights.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -111,6 +111,8 @@ Vite `?url` import 로 로드됩니다.
 | Model + Paper 동시 렌더로 글자 겹침 / Layout 탭 | [`docs/model-paper-space.md`](./docs/model-paper-space.md) |
 | `dist2` 정적 빌드 배포 절차 (공식 배포 스크립트 없음) | [`docs/deploy-dist2-static-build.md`](./docs/deploy-dist2-static-build.md) |
 | SubDMesh(MESH) 미표시 — parseResult 누락 + 큰 메쉬 잘림 | [`docs/subdmesh-rendering.md`](./docs/subdmesh-rendering.md) |
+| 선가중치(Lineweight) 미적용 — parseResult 누락 + WebGL 1px 한계 | [`docs/lineweight-rendering.md`](./docs/lineweight-rendering.md) |
+| ↳ 위 둘의 측정 결과 + 상호작용(메쉬 선분이 굵기 버킷 상한을 넘길 위험) | [`docs/improvement-results-2026-08-04.md`](./docs/improvement-results-2026-08-04.md) |
 
 샘플 패치: `fixDwgKoreanText`, `cadSpaces` + Viewer2D 공간 필터, Model/Layout 탭.  
 원본 `hmwebviewer` 반영 절차는 각 문서를 따른다.