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.

.agents/skills/halo-theme-dev/assets/theme-vite/settings.yaml

@@ -0,0 +1,14 @@
+apiVersion: v1alpha1
+kind: Setting
+metadata:
+  name: theme-vite-setting
+spec:
+  forms:
+    - group: basic
+      label: Basic Settings
+      formSchema:
+        - $formkit: text
+          name: custom_footer
+          label: Custom footer text
+          value: ""
+          placeholder: "e.g. Copyright © 2024 My Site"