feat: migrate 12 personal skills + add build/install scripts

- skills/: editable sources for all 12 personal skills (caveman family,
  find-skills, project-bootstrap, task-status-wiki, using-context7,
  using-markitdown, wiki-maintainer, compress)
- dist/: built .skill archives, committed (cross-machine deploy without
  needing zip on the target)
- scripts/build.sh + build.ps1: zip skills/<name>/ into dist/<name>.skill;
  Windows fallback uses .NET ZipArchive (PS 5.1 Compress-Archive writes
  backslashes that break extraction on *nix)
- scripts/install.sh: copy skills/<name>/ into ~/.claude/skills/<name>/
  ($CLAUDE_SKILLS_DIR overrides target)
- .wiki/source/repo-layout.md, build-notes.md: design + gotchas
- .gitignore: keep dist/ tracked

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -19,7 +19,7 @@ env/
 .ruff_cache/
 
 # Build output
-dist/
+# (dist/ is intentionally NOT ignored — we commit built .skill archives)
 build/
 out/
 target/