feat: implement dynamic Eleventy tiling blog, modular CSS, and agent customizations

- Add project foundation README.md and root AGENTS.md for pair programming
- Configure .agents/ rules and skills for Eleventy tiling and Obsidian publishing
- Decompose monolithic styles into modular tokens, reset, layout, and component CSS
- Implement Nunjucks layout inheritance (base.njk, post.njk, page.njk) and reusable partials
- Configure Eleventy 3 with markdown-it-anchor, syntax highlighting, and dynamic collections
- Migrate sample prototypes into dynamic dispatches lander, gateway, and Markdown posts
- Add multi-stage Dockerfile and clean-URL nginx.conf for production serving

src/assets/css/main.css

@@ -0,0 +1,21 @@
+/* ==========================================================================
+   Main Stylesheet (main.css)
+   River Rooks Blog - Modular CSS Architecture
+   ========================================================================== */
+
+/* 1. Design Tokens & CSS Custom Properties */
+@import "./tokens.css";
+
+/* 2. Global Reset & Baseline Typography */
+@import "./reset.css";
+
+/* 3. Tiling Window Manager Grids */
+@import "./layout.css";
+
+/* 4. Component Styles */
+@import "./components/global-bar.css";
+@import "./components/tiles.css";
+@import "./components/cards.css";
+@import "./components/code-box.css";
+@import "./components/article.css";
+@import "./components/footer.css";