fix(input): update disabled opacity of md input (#26514)

core/src/components/input/input.md.scss

@@ -34,6 +34,13 @@
   height: 22px;
 }
 
+// Input - Disabled
+// ----------------------------------------------------------------
+:host(.legacy-input) .native-input[disabled],
+:host([disabled]) {
+  opacity: #{$input-md-disabled-opacity};
+}
+
 // Input Bottom
 // ----------------------------------------------------------------
 /**

core/src/components/input/input.md.vars.scss

@@ -69,3 +69,8 @@ $input-md-inset-margin-start:             $item-md-padding-start !default;
 
 /// @prop - The amount of whitespace to display on either side of the floating label
 $input-md-floating-label-padding: 4px !default;
+
+/// @prop - The disabled opacity of the input text, the label, helper text, char counter and placeholder of a disabled input.
+/// This value comes from the Material Design spec:
+/// - https://github.com/material-components/material-web/pull/549
+$input-md-disabled-opacity: 0.37 !default;

core/src/components/input/input.vars.scss

@@ -2,3 +2,4 @@
 
 /// @prop - How much to scale the floating label by
 $input-floating-label-scale: 0.75 !default;
+