chore: record journal

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

@@ -68,3 +68,24 @@ Moved durable conclusions from the temporary osmassets refactor plan into change
 ### Status
 
 [OK] **Completed**
+
+
+## Session 4: Extract fountain module
+
+**Date**: 2026-08-03
+**Task**: Extract fountain module
+**Branch**: `main`
+
+### Summary
+
+Moved fountain assembly from generate_scene.py into blender/osmassets/fountain.py, updated P2 refactor docs, and verified py_compile, 51 pure tests, and Blender/Cesium parity before/after with identical snapshots.
+
+### Git Commits
+
+| Hash | Message |
+|------|---------|
+| `6271055` | (see git log) |
+
+### Status
+
+[OK] **Completed**