add custom website build system

Replaces MkDocs with a bespoke Python site generator using Jinja2 templates
and Markdown. Adds uv for dependency management, GitHub Actions workflow for
deployment, and Makefile targets for local development (fetch_stars, build,
preview, deploy).

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

.gitignore

@@ -1,9 +1,15 @@
+# macOS
 .DS_Store
 
+# python
+.venv/
 *.py[co]
 
-docs/index.md
-site/
+# website
+website/output/
 
-# PyCharm IDE
-.idea
+# claude code
+.claude/skills/
+.superpowers/
+.gstack/
+skills-lock.json