Add halo-theme-dev skill & theme templates

Add a new .agents/skills/halo-theme-dev skill providing Halo theme development resources: two theme templates (theme-vite and theme-minimal) with theme.yaml/settings, Vite config, package.json, CSS and JS assets, and a full set of Thymeleaf template files/partials. Include comprehensive reference docs (structure & config, finder APIs, global variables, annotations, static resources, packaging, official plugins, thymeleaf tips) and an agents/openai.yaml interface. Also update project files: modify package.json, update tsconfig.json, add skills-lock.json, rename vite-env.d.ts and remove obsolete src/main.ts and src/styles/main.css while populating src/ with the new template files.

src/partials/post-card.html

@@ -0,0 +1,18 @@
+<li class="post-item" th:each="post : ${posts.items}">
+  <h2 class="post-title">
+    <a th:href="@{${post.status.permalink}}" th:text="${post.spec.title}"></a>
+  </h2>
+  <p class="post-meta">
+    <time th:text="${#temporals.format(post.spec.publishTime, 'yyyy-MM-dd')}"></time>
+    <span th:if="${not #lists.isEmpty(post.categories)}">
+      &nbsp;·&nbsp;
+      <a
+        th:each="cat : ${post.categories}"
+        th:href="@{${cat.status.permalink}}"
+        th:text="${cat.spec.displayName}"
+        class="category"
+      ></a>
+    </span>
+  </p>
+  <p class="post-excerpt" th:text="${post.status.excerpt}"></p>
+</li>