feat: adapt CustomSelect styles to native select ::picker pseudo-element (#5585)

* Initial plan

* feat: adapt CustomSelect styles to native select picker

Co-authored-by: mfranzke <787658+mfranzke@users.noreply.github.com>

* refactor: remove redundant overflow-y property

Co-authored-by: mfranzke <787658+mfranzke@users.noreply.github.com>

* docs: improve comments for option height calculation

Co-authored-by: mfranzke <787658+mfranzke@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: GitHub Copilot <copilot@github.com>
Co-authored-by: mfranzke <787658+mfranzke@users.noreply.github.com>

Author: 3 people

packages/components/src/components/select/select.scss

@@ -3,6 +3,7 @@
 @use "@db-ux/core-foundations/build/styles/colors";
 @use "@db-ux/core-foundations/build/styles/icons";
 @use "@db-ux/core-foundations/build/styles/fonts";
+@use "@db-ux/core-foundations/build/styles/helpers";
 @use "../../styles/internal/form-components";
 @use "../../styles/internal/component";
 @use "../../styles/internal/select-components";
@@ -67,18 +68,64 @@
 		/* stylelint-disable-next-line selector-pseudo-element-no-unknown */
 		:is(::picker(select)) {
 			@extend %default-card;
+
+			// Adapted from .db-custom-select-dropdown
+			position: absolute;
+			z-index: 32;
+			box-shadow: variables.$db-elevation-md;
+			min-inline-size: variables.$db-sizing-xl;
+			max-inline-size: calc(
+				100vw - 2 * #{variables.$db-spacing-fixed-sm}
+			);
+
+			// Adapted from .db-card
+			background-color: colors.$db-adaptive-bg-basic-level-1-default;
+			padding: variables.$db-spacing-fixed-sm;
+
+			// Adapted from .db-custom-select-list
+			overflow-block: auto;
+
+			/* (option height + padding) * 5.5 items (showing partial item to indicate more content) + list padding */
+			max-block-size: calc(
+				5.5 *
+					(
+						(
+								#{form-components.$font-size-height} - 2 *
+									#{variables.$db-border-width-3xs}
+							) +
+							2 * #{variables.$db-spacing-fixed-sm}
+					) +
+					(#{variables.$db-spacing-fixed-sm} * 2)
+			);
 		}
 
 		option {
+			// Adapted from .db-custom-select-list-item
+			position: relative;
+			padding: variables.$db-spacing-fixed-sm;
+			background-color: colors.$db-adaptive-bg-basic-transparent-full-default;
+			border-radius: variables.$db-border-radius-xs;
+			box-sizing: border-box;
 			justify-content: space-between;
-			
+
 			// change order of the included text and pseudo-element within this flexbox item, to make sure the icon is always on the right
 			flex-direction: row-reverse;
 
 			&:checked {
 				font-weight: 700;
 			}
 
+			// Hover states adapted from .db-custom-select-list-item
+			&:not(:checked) {
+				@include helpers.hover {
+					background-color: colors.$db-adaptive-bg-basic-transparent-full-hovered;
+				}
+
+				@include helpers.active {
+					background-color: colors.$db-adaptive-bg-basic-transparent-full-pressed;
+				}
+			}
+
 			/* stylelint-disable-next-line selector-pseudo-element-no-unknown */
 			:is(&::checkmark) {
 				@extend %icon;