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>

Colosseum.slnx

@@ -1,5 +1,9 @@
 <Solution>
   <Project Path="Assembly-CSharp.csproj" />
   <Project Path="Colosseum.Game.csproj" />
+  <Project Path="SidekickCharacters.csproj" />
+  <Project Path="Gilzoide.SqliteNet.csproj" />
   <Project Path="Assembly-CSharp-Editor.csproj" />
+  <Project Path="SidekickCharacters.Editor.csproj" />
+  <Project Path="Gilzoide.SqliteNet.Tests.Editor.csproj" />
 </Solution>