feat(examples): add hemx html pattern gallery

Add examples/html_examples as a copy-pasteable gallery for the first htmx-style HTML UX patterns using exact htmx URL slugs in the page and README. The slice covers click-to-edit, edit-row, delete-row, inline-validation, click-to-load, and active-search with .heml templates, generated resources, server-owned Rust state, and runtime-free selector targeting.

req: htmx_equivalents/001

req: htmx_equivalents/002

req: examples/001

examples/html_examples/templates/partials/contact_card.heml

@@ -0,0 +1,15 @@
+<article +data-key="self.id">
+  <div h-if="!self.editing">
+    <h3>{+ self.name +}</h3>
+    <p>{+ self.email +}</p>
+    <form data-hemx-handle="edit_contact" data-hemx-form="edit_contact">
+      <button type="submit" name="id" +value="self.id">Edit</button>
+    </form>
+  </div>
+  <form h-if="self.editing" data-hemx-handle="save_contact" data-hemx-form="save_contact">
+    <input type="hidden" name="id" +value="self.id">
+    <label>Name <input name="name" +value="self.name" required="required"></label>
+    <label>Email <input name="email" +value="self.email" required="required"></label>
+    <button type="submit">Save</button>
+  </form>
+</article>