chore: .gitignore, 씬 및 UI/무기 디렉토리 업데이트

- .gitignore: External packages, Sketchfab, Wwise 무시 추가
- Colosseum.slnx: 솔루션 파일 업데이트
- Test.unity: 게임 매니저 및 UI 연동
- UI/, Weapons/ 디렉토리 추가

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

.gitignore

@@ -74,3 +74,16 @@ crashlytics-build.properties
 /[Aa]ssets/[Ss]treamingAssets/aa/*
 
 .vscode
+
+
+# External packages (not tracked)
+Assets/External/SidekickCharacters/
+Assets/External/SyntyPackageHelper 1/
+Assets/DownloadCache/
+
+# Sketchfab files
+Assets/External_Used/Models/Human-Custom.sk
+Assets/External_Used/Models/Human-Custom.sk.meta
+
+# Wwise audio project
+Colosseum.slnx