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>

.github/workflows/deploy-website.yml

@@ -0,0 +1,48 @@
+name: Deploy Website
+
+on:
+  push:
+    branches:
+      - master
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          enable-cache: true
+
+      - name: Install dependencies
+        run: uv sync --no-dev
+
+      - name: Build site
+        run: uv run python website/build.py
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: website/output/
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4