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>

.wiki/source/build-notes.md

@@ -0,0 +1,36 @@
+# Build Notes
+
+Practical gotchas around building `.skill` archives.
+
+## Why `build.ps1` exists alongside `build.sh`
+
+The user is on Windows; the install target may be Linux/macOS. So archives must be portable.
+
+**Windows PowerShell 5.1's `Compress-Archive` (v1.0.1.0) writes ZIP entries with backslashes** (e.g. `caveman\SKILL.md`). Linux/macOS `unzip` then either fails or extracts the literal name as a single file. Verified: archives produced by `Compress-Archive` listed entries like `caveman\SKILL.md`.
+
+Workarounds considered:
+- Install `zip.exe` → adds a Windows dep we don't want.
+- PowerShell 7's `Compress-Archive` is fixed → can't assume PS7 is installed.
+- **Use .NET `System.IO.Compression.ZipArchive` directly** ← chosen. Walks files, adds entries with `path -replace '\\','/'`. Spec-compliant ZIPs everywhere.
+
+`build.ps1` does that. `build.sh` prefers `zip` (one-liner, fast on *nix), and on Windows-without-`zip` it falls back to invoking `build.ps1` via `powershell.exe`.
+
+## ZIP layout the loader expects
+
+Looking at the canonical `~/.claude/skills/<name>/` layout, the `.skill` archive should contain a single top-level directory `<name>/` with `SKILL.md` plus optional `assets/`, `references/`, etc. inside.
+
+`zip -qr dist/<name>.skill <name>` (run from `skills/`) does this naturally. The .NET path adds an explicit `<name>/` prefix to each entry.
+
+## Extracting `.skill` files
+
+A `.skill` file is just a renamed `.zip`. To extract on Windows:
+
+```powershell
+Copy-Item project-bootstrap.skill project-bootstrap.zip
+Expand-Archive -Path project-bootstrap.zip -DestinationPath ~/.claude/skills/
+Remove-Item project-bootstrap.zip
+```
+
+On *nix: `unzip dist/project-bootstrap.skill -d ~/.claude/skills/`.
+
+(Our `install.sh` skips this entirely — it copies from `skills/` directly. Extraction-from-archive is only needed when you don't have the source tree, e.g. when sharing a single `.skill` file with someone else.)