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>

CLAUDE.md

@@ -20,7 +20,6 @@
 4. `docs/SCENARIO.md` — 요구사항 + **핵심 사용자 여정**(§4.5)
 5. `docs/ARCHITECTURE.md` — 스택·데이터흐름·DB/AI/APO/공유(.tweq) 스키마
 6. `docs/TYPOGRAPHY.md` — 폰트 규칙(최소 12·최대 24, 가독성 우선)
-7. `mockups/gallery.html` — 전체 UI 목업(브라우저로 열기)
 
 ## 다음 세션 첫 작업 (순서)
 1. **솔루션·빌드·테스트**