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>

.gitignore

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+# ===== Unity =====
+
+# Unity generated
+/[Ll]ibrary/
+/[Tt]emp/
+/[Oo]bj/
+/[Bb]uild/
+/[Bb]uilds/
+/[Ll]ogs/
+/[Uu]ser[Ss]ettings/
+
+# MemoryCaptures
+/[Mm]emoryCaptures/
+
+# Recordings
+/[Rr]ecordings/
+
+# Asset meta data should only be ignored when the corresponding asset is also ignored
+!/[Aa]ssets/**/*.meta
+
+# Autogenerated Lighting data
+**/[Ll]ightingData.asset
+**/[Ll]ightingData.asset.meta
+
+# Autogenerated VS/MD/Consoles solution and target files
+ExportedObj/
+.consulo/
+*.csproj
+*.unityproj
+*.sln
+*.suo
+*.tmp
+*.user
+*.userprefs
+*.pidb
+*.booproj
+*.svd
+*.pdb
+*.mdb
+*.opendb
+*.VC.db
+
+# Unity3D generated meta files
+*.pidb.meta
+*.pdb.meta
+*.mdb.meta
+
+# Unity3D generated file on crash reports
+sysinfo.txt
+
+# Builds
+*.apk
+*.aab
+*.unitypackage
+*.app
+
+# Crashlytics generated file
+crashlytics-build.properties
+
+# ===== IDE =====
+
+# JetBrains Rider
+.idea/
+
+# Visual Studio
+.vs/
+
+# Visual Studio Code
+.vscode/
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+
+# ===== OS =====
+
+# macOS
+.DS_Store
+.AppleDouble
+.LSOverride
+Icon?
+._*
+
+# Windows
+Thumbs.db
+ehthumbs.db
+Desktop.ini
+
+# ===== Misc =====
+
+# Nuget
+/[Pp]ackages/nuget/
+*.nupkg
+
+# Secrets / env
+.env
+.env.*
+*.key
+*.pem