Add pawn utility-AI brain; format code with CSharpier; enforce formatter

Wire the engine's new MrGameEng.AI module into a PawnBrain for world pawns,
plus surrounding content/scene tweaks. Apply CSharpier across the game and
document the convention in CLAUDE.md. Add .vscode/settings.json so the editor
formats on save with the CSharpier extension.

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "editor.defaultFormatter": "csharpier.csharpier-vscode",
+    "editor.formatOnPaste": true,
+    "editor.formatOnSave": true
+}