fix: return createBlock instances from block transforms and fix filter CSS selectors

Two related bug fixes:

- Transforms: `type: 'block'` callbacks must return a block instance created by createBlock; the previous code returned raw attribute objects which WordPress silently ignored, so the toolbar block-switcher transforms never fired. Update tests to assert on `result.name` and `result.attributes`. Add a manual jest mock for @wordpress/blocks since the package is provided at runtime via dependency-extraction-webpack-plugin.

- Filter CSS: the SCSS used a descendant combinator (`.wp-block-ksolo-image-filter .has-filter-warm img`) but the JSX puts both classes on the same element, so the filter rule never matched and picking a filter had no visual effect on the editor or the front end. Target the inner <img> by its stable class pair (`.ksolo-image-filter-img.has-filter-<slug>`) instead. Add a regression test that reads the compiled CSS and asserts the selectors are present for every preset.

src/transforms.js

@@ -5,9 +5,14 @@
  * - "From" core Image: copies image attributes, sets filter="normal",
  *   intensity=100.
  *
+ * Per the Block Transforms API, `type: 'block'` transforms must return a
+ * block instance produced by `createBlock` from `@wordpress/blocks` — a
+ * raw attribute object is silently ignored and the transform fails.
+ *
  * @package SoloFiltersImageEnhancements
  */
 
+import { createBlock } from '@wordpress/blocks';
 import { DEFAULT_PRESET } from './presets';
 
 const IMAGE_ATTR_MAP = {
@@ -69,16 +74,18 @@ export const transforms = {
         {
             type: 'block',
             blocks: [ 'core/image' ],
-            transform: ( attributes ) => toImageAttrs( attributes ),
+            transform: ( attributes ) =>
+                createBlock( 'core/image', toImageAttrs( attributes ) ),
         },
     ],
     from: [
         {
             type: 'block',
             blocks: [ 'core/image' ],
-            transform: ( attributes ) => fromImageAttrs( attributes ),
+            transform: ( attributes ) =>
+                createBlock( 'ksolo/image-filter', fromImageAttrs( attributes ) ),
         },
     ],
 };
 
-export default transforms;
+export default transforms;