Clean up repo: prune non-dev assets, redirect build output, add .gitignore

- Remove old/unneeded material: mockups/, docs/Image (ChatGPT imgs·GIFs),
  character art docs (IMAGE_GEN_*, *.md.old, BRAND_CHARACTERS, CHARACTER_PROFILES),
  asset backups (Characters_OriginalBackup, SourceCandidates),
  unused puppet variants (LeeSoriExtended/Regenerated/Upper/V2/V3), tools/ art scripts
- Keep active assets only: LeeSori + LeeSoriDance puppets, Live2DPreview, Live2DHost, mascot PNGs
- Fix dangling references in kept docs (README, CLAUDE, ARCHITECTURE, TYPOGRAPHY, CHARACTER_UI_INTEGRATION)
- Refresh HANDOFF.md to live state (LeeSoriDance puppet, D:\Project paths)
- Redirect all build output to Build/ via Directory.Build.props (bin+obj)
- Add .gitignore and untrack previously committed bin/obj artifacts

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -42,8 +42,7 @@ DansoriEQ/
 ├─ src/DansoriEQ.Core/     # 순수 로직(EQ 수학·모델·APO 렌더·AI 스키마·프리셋·스위칭)
 ├─ src/DansoriEQ.App/      # WPF 앱(창·컨트롤·서비스: Apo/Ai/Audio/Switching/Profiles …)
 ├─ tests/DansoriEQ.Core.Tests/  # 단위테스트(Filter 수학·파서·직렬화·이펙트 렌더)
-├─ docs/                   # SCENARIO / ARCHITECTURE / DEV_PLAN / TYPOGRAPHY / PREBUILT
-└─ mockups/                # gallery.html (전체 화면 비주얼 목표)
+└─ docs/                   # SCENARIO / ARCHITECTURE / DEV_PLAN / HANDOFF / TYPOGRAPHY / PREBUILT
 ```
 
 ## 빌드 & 실행 (개발 세션)
@@ -70,7 +69,6 @@ dotnet run --project src/DansoriEQ.App
 - `docs/DEV_PLAN.md` — 마일스톤·잔여 작업
 - `docs/TYPOGRAPHY.md` — 타이포그래피 규칙(가독성 우선)
 - `docs/PREBUILT.md` — 선생성 코드 목록·교체 지점
-- `mockups/gallery.html` — 전체 UI 목업
 
 ## 라이선스
 미정(TBD). AutoEQ 등 측정 데이터는 각 출처 라이선스를 따르며, 배포 불가 소스는 배포 빌드에서 제외합니다(`--exclude-restricted`).