feat: split non-pattern components (pavement, base, drains, 공동구) at pattern-run boundaries (Task 8)

- build_solids.py: PAV/BASE/DRNL/DRNR/HBOX/IBOX are now built per pattern run
  instead of 100 m chunks, so each solid carries its run's pattern and station range.
- Rebuilt GLB (326 geometries), meta and verify (320 solids, volume sum 12406.138 m3).

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A5Cun3RHQKna9qxE6ybZ4A

data/verify_solids.json

@@ -1,13 +1,13 @@
 {
-  "solid_count": 128,
+  "solid_count": 320,
   "runs": 40,
   "pattern_coverage": "4745..5480 contiguous",
   "lining_runs": 40,
   "excavation_runs": 40,
-  "volume_sum_m3": 12406.136,
-  "step_bytes": 84621457,
-  "glb_bytes": 1287912,
-  "glb_geometries": 134,
+  "volume_sum_m3": 12406.138,
+  "step_bytes": 91713125,
+  "glb_bytes": 1566612,
+  "glb_geometries": 326,
   "section_overlap_m2_by_station": {
     "4745": {
       "lining_vs_excavation": 0.01732111,