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/_includes/partials/post-card.njk

@@ -0,0 +1,27 @@
+<article class="feed-card" aria-labelledby="post-title-{{ post.fileSlug }}">
+  <div class="feed-meta-row">
+    <time class="feed-date" datetime="{{ post.date | isoDate }}">
+      {{ post.date | postDate }}
+    </time>
+    <span>{{ post.templateContent | readingTime(post.data.readingTime) }}</span>
+  </div>
+
+  <h3 id="post-title-{{ post.fileSlug }}">
+    <a href="{{ post.url }}" class="feed-heading">{{ post.data.title }}</a>
+  </h3>
+
+  {% if post.data.excerpt %}
+    <p class="feed-excerpt">{{ post.data.excerpt }}</p>
+  {% endif %}
+
+  <div class="feed-tags-row">
+    <div class="tag-cluster">
+      {% for tag in post.data.tags | filterTagList %}
+        <span class="tag-chip">#{{ tag }}</span>
+      {% endfor %}
+    </div>
+    {% if post.data.difficulty %}
+      <span>DIFFICULTY: {{ post.data.difficulty }}</span>
+    {% endif %}
+  </div>
+</article>