feat(slint): search loading fade + 1s idle-close on header menus

New LoadingDots primitive (three pulsing dots over an optional label)
shown while a search is running. The result sections fade in once the
results arrive instead of showing empty placeholder colors. The
LoadingDots component is reusable for other heavy loads (large grids,
playlist manager) when they get the same treatment.

The header nav-tab menu now closes after 1s of pointer idle (was 1.5s)
per the project rule that no menu stays open more than 1s idle.
PopupWindow context menus already close on click-outside, which is the
idle behaviour for click-triggered popups.

cc

crates/qbz-slint/ui/search/SearchResultsView.slint

@@ -21,6 +21,7 @@ import { PlaylistCard } from "../discover/PlaylistCard.slint";
 import { SearchTrackRow } from "SearchTrackRow.slint";
 import { NavButtons } from "../shell/NavButtons.slint";
 import { QbzIcon } from "../primitives/QbzIcon.slint";
+import { LoadingDots } from "../primitives/LoadingDots.slint";
 
 // One tab in the results tab strip.
 component SearchTab inherits Rectangle {
@@ -425,9 +426,19 @@ export component SearchResultsView inherits Rectangle {
                 padding-left: 32px;
                 padding-right: 32px;
                 padding-bottom: 32px;
-                spacing: 28px;
+                spacing: 0px;
                 alignment: start;
 
+                // Results sections — fade in once the search completes
+                // so the empty placeholder colors never show through.
+                VerticalLayout {
+                    spacing: 28px;
+                    opacity: SearchState.loading ? 0.0 : 1.0;
+                    animate opacity {
+                        duration: 280ms;
+                        easing: ease-in-out;
+                    }
+
                 // ---- Most popular + Artists (All tab) ---------------------
                 if SearchState.tab == 0 && SearchState.most-popular-kind != "": HorizontalLayout {
                     spacing: 24px;
@@ -571,11 +582,11 @@ export component SearchResultsView inherits Rectangle {
                     clicked => { SearchActions.load-more(4); }
                 }
 
-                // ---- Empty / loading state --------------------------------
-                if SearchState.loading && !root.has-results: Text {
-                    text: @tr("Searching…");
-                    color: Theme.text-muted;
-                    font-size: 14px;
+                }
+                // ---- Loading + empty states -------------------------------
+                if SearchState.loading && !root.has-results: LoadingDots {
+                    label: @tr("Searching…");
+                    height: 140px;
                 }
                 if !SearchState.loading && !root.has-results: Text {
                     text: @tr("No results.");