Use the wp-admin sass mixin for the WP 7.0 field styles

Mirrors upstream's nested @include wp-admin("7-0") structure instead of
flat compiled-style selectors. Brings _mixins.scss into the build via
@use; compiled output is unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: ockham

assets/src/sass/acf-input.scss

@@ -1,4 +1,5 @@
 @charset "UTF-8";
+@use "mixins" as *;
 /*--------------------------------------------------------------------------------------------
 *
 *	Vars
@@ -586,10 +587,13 @@ body.acf-browser-firefox .acf-field select {
   border-color: #dddddd;
   min-height: 28px;
 }
-.acf-admin-7-0 .acf-input-prepend,
-.acf-admin-7-0 .acf-input-append {
-  min-height: 40px;
-  padding: 9px 8px;
+.acf-input-prepend,
+.acf-input-append {
+  // WP 7.0+
+  @include wp-admin("7-0") {
+    min-height: 40px;
+    padding: 9px 8px;
+  }
 }
 
 .acf-input-prepend {
@@ -743,8 +747,11 @@ html[dir=rtl] input.acf-is-prepended.acf-is-appended {
   box-shadow: 0 1px 2px rgba(0, 0, 0, 0.07) inset;
   min-height: 31px;
 }
-.acf-admin-7-0 .select2-container.-acf .select2-choices {
-  min-height: 40px;
+.select2-container.-acf .select2-choices {
+  // WP 7.0+
+  @include wp-admin("7-0") {
+    min-height: 40px;
+  }
 }
 .select2-container.-acf .select2-choices .select2-search-choice {
   margin: 5px 0 5px 5px;
@@ -848,30 +855,40 @@ html[dir=rtl] .select2-container.-acf .select2-choice .select2-arrow {
 .acf-admin-3-8 .select2-container.-acf .select2-selection {
   border-color: #aaa;
 }
-.acf-admin-7-0 .select2-container.-acf .select2-selection--single {
-  height: 40px;
-}
-.acf-admin-7-0 .select2-container.-acf .select2-selection--single .select2-selection__rendered {
-  line-height: 38px;
-}
-.acf-admin-7-0 .select2-container.-acf .select2-selection--multiple {
-  min-height: 40px;
-  line-height: 0;
-}
-.acf-admin-7-0 .select2-container.-acf .select2-selection--multiple .select2-selection__rendered {
-  line-height: normal;
-  display: flex;
-  align-items: center;
-  flex-wrap: wrap;
-  min-height: 38px;
-}
-.acf-admin-7-0 .select2-container.-acf .select2-selection--multiple .select2-search__field {
-  margin-top: 0;
-}
-.acf-admin-7-0 .select2-container.-acf .select2-selection--multiple .select2-selection__choice {
-  margin-top: 0;
-  padding-top: 4px;
-  padding-bottom: 4px;
+.select2-container.-acf {
+  // WP 7.0+
+  @include wp-admin("7-0") {
+    .select2-selection--single {
+      height: 40px;
+
+      .select2-selection__rendered {
+        line-height: 38px;
+      }
+    }
+
+    .select2-selection--multiple {
+      min-height: 40px;
+      line-height: 0;
+
+      .select2-selection__rendered {
+        line-height: normal;
+        display: flex;
+        align-items: center;
+        flex-wrap: wrap;
+        min-height: 38px;
+      }
+
+      .select2-search__field {
+        margin-top: 0;
+      }
+
+      .select2-selection__choice {
+        margin-top: 0;
+        padding-top: 4px;
+        padding-bottom: 4px;
+      }
+    }
+  }
 }
 .select2-container.-acf .select2-selection--multiple .select2-search--inline:first-child {
   float: none;