Add chips, choices and search

M3's assist, filter, input and suggestion chips with chip sets; choices
as filter chips or a searchable combobox whose list is an anchored
popover; and the search bar that opens into a docked or full-screen
search view.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V9NnLxnPp8vaaurb3Z1MFy

resources/css/components/menu.css

@@ -29,6 +29,25 @@
     box-shadow: var(--md-sys-elevation-2);
 }
 
+/* As a popover (`<x-choices searchable>`), it hangs under its field, as wide, and goes above only
+   when there is no room below. */
+.field-menu[popover] {
+    inset: auto;
+    top: anchor(bottom);
+    left: anchor(left);
+    width: anchor-size(width);
+    margin: 0.25rem 0;
+    border: 0;
+    padding-inline: 0;
+    color: var(--md-sys-color-on-surface);
+    position-try-fallbacks: flip-block;
+}
+
+.field-option[aria-disabled="true"] {
+    color: color-mix(in srgb, var(--md-sys-color-on-surface) 38%, transparent);
+    cursor: default;
+}
+
 .field-option {
     display: flex;
     align-items: center;