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/tag.html

@@ -0,0 +1,13 @@
+<include src="layout.html">
+  <template name="head">
+    <title th:text="|${tag.spec.displayName} - ${site.title}|">Tag Archive</title>
+  </template>
+
+  <h1 th:text="|Tag: ${tag.spec.displayName}|"></h1>
+
+  <ul class="post-list">
+    <include src="post-card.html"></include>
+  </ul>
+
+  <include src="pagination.html"></include>
+</include>