Replace the .form migration snippet that fails in Tailwind v4

Tailwind v4 can't @apply Basecoat's component classes, so the 1.0.0 migration snippet failed with "Cannot apply unknown utility class". Show the .field wrapper and the per-element classes instead.

CHANGELOG.md

@@ -156,15 +156,17 @@
 
 ### Migration Notes
 
-To keep the previous `.form` wrapper behavior, define it in your own Tailwind CSS:
+The `.form` wrapper can't be recreated with `@apply`: Tailwind v4 only applies utilities, not Basecoat's component classes. Wrap each label and control in a `.field` instead:
 
-```css
-.form label { @apply label; }
-.form input { @apply input; }
-.form textarea { @apply textarea; }
-.form select { @apply select; }
+```html
+<div class="field">
+  <label for="email">Email</label>
+  <input id="email" type="email">
+</div>
 ```
 
+Or add the component class to each element: `class="label"`, `class="input"`, `class="textarea"`, or `class="select"` on a native `<select>`.
+
 To keep the previous document-event command APIs, add bridge listeners in your app:
 
 ```js