init: Unity 6 프로젝트 초기 설정

Unity 6000.4.0f1, URP 2D 프로젝트 초기 구조.
CLAUDE.md, .gitignore 포함.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ProjectSettings/AudioManager.asset

@@ -0,0 +1,19 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!11 &1
+AudioManager:
+  m_ObjectHideFlags: 0
+  serializedVersion: 2
+  m_Volume: 1
+  Rolloff Scale: 1
+  Doppler Factor: 1
+  Default Speaker Mode: 2
+  m_SampleRate: 0
+  m_DSPBufferSize: 1024
+  m_VirtualVoiceCount: 512
+  m_RealVoiceCount: 32
+  m_SpatializerPlugin: 
+  m_AmbisonicDecoderPlugin: 
+  m_DisableAudio: 0
+  m_VirtualizeEffects: 1
+  m_RequestedDSPBufferSize: 0