chore: add .gitignore to exclude dev folders

Added .gitignore to exclude local development folders:
- .vscode/
- node_modules/
- build/
- src/territorial/ (used for local analysis)

This helps avoid accidental commits of non-source files.

.gitignore

@@ -1,4 +1,6 @@
 .vscode
 node_modules
 game
-build
+build
+# ↓ 以下是我本地用的私有开发路径（不包含在 PR 中）
+dev/