chore: record journal

.trellis/workspace/dingkang/journal-1.md

@@ -89,3 +89,24 @@ Moved fountain assembly from generate_scene.py into blender/osmassets/fountain.p
 ### Status
 
 [OK] **Completed**
+
+
+## Session 5: Extract building module
+
+**Date**: 2026-08-03
+**Task**: Extract building module
+**Branch**: `main`
+
+### Summary
+
+Moved building assembly from generate_scene.py into blender/osmassets/building.py, updated P2 refactor docs so only roads remains in generate_scene.py, and verified py_compile, 51 pure tests, and Blender/Cesium parity before/after with identical snapshots.
+
+### Git Commits
+
+| Hash | Message |
+|------|---------|
+| `032922a` | (see git log) |
+
+### Status
+
+[OK] **Completed**