Consolidate all moonweb sites into single Eleventy config

- Single eleventy.config.js at root with computed pathPrefix per section
- Accent colors inlined in base.njk (no per-site theme.css needed)
- Hub pages output at root via explicit permalinks
- Per-section sitemaps with tag-based collections
- .eleventyignore excludes stefankoelle, timecapsule, markdown files
- Deleted: 5 per-site configs, merge script
- Simplified: package.json (single build/dev commands)
- Simplified: GitHub Actions workflow (no matrix, no merge job)
- Fixed: parent links for sub-site detail pages

retro/mist-mister-fpga/index.njk

@@ -1,9 +1,10 @@
 ---
 title: "MiST and MiSTer: Two FPGA Boxes, Two Very Different Personalities"
 section: "retro"
+tags: "retro"
 description: "Why the newer, more powerful MiSTer isn't automatically the better choice for every retro system."
 layout: base.njk
-parent: "/"
+parent: "/retro/"
 ---
 <h1>MiST and MiSTer: Two FPGA Boxes, Two Very Different Personalities</h1>
 <div class="detail-content">