feat(ui): add the Vue component kit with UiRail, UiTooltip and UiIcon

src/ui/kit/rail.js

@@ -0,0 +1,12 @@
+/**
+ * @typedef {object} UiRailItem
+ * @property {string} id Item identity, emitted on selection.
+ * @property {string} label Translated name, shown as the tooltip and accessible name.
+ * @property {string} icon Material Symbols glyph.
+ * @property {boolean} [disabled] Shown but not selectable.
+ * @property {boolean} [separatorBefore] Draw a divider above this item.
+ * @property {string|number} [badge] Small count or marker on the icon.
+ */
+
+/** How long the pointer rests on an item before its tip shows over an open panel. */
+export const RAIL_PANEL_OPEN_TOOLTIP_DELAY_MS = 400;