fix(material/core): add key validation to m2-theme (#31631)

* fix(material/core): add key validation to m2-theme

* refactor: lint

Author: andrewseguin

src/material/core/tokens/_system.scss

@@ -24,6 +24,7 @@
 @use '../style/sass-utils';
 @use './m2';
 @use './m3';
+@use 'sass:list';
 @use 'sass:map';
 @use 'sass:meta';
 
@@ -328,6 +329,20 @@
         'configs created with define-light-theme or define-dark-theme';
   }
 
+  // Check whether any override keys do not match keys in the theme
+  // config system map.
+  $invalid-keys: ();
+  $config-system: map.get($theme-config, _mat-system);
+  @each $key, $value in $overrides {
+    @if (not map.has-key($config-system, $key)) {
+      $invalid-keys: list.append($invalid-keys, $key);
+    }
+  }
+  @if (list.length($invalid-keys) > 0) {
+    @error 'The following overrides are not valid system variables: #{$invalid-keys}. ' +
+        'Valid keys are: #{map.keys($config-system)}';
+  }
+
   $config: m2-inspection.get-m2-config($theme-config);
 
   $color: map.get($config, color);