feat(FontVirtualList): re-touch on weight change and pin visible fonts

src/entities/Font/ui/FontVirtualList/FontVirtualList.svelte

@@ -18,8 +18,8 @@ import {
     type FontLoadRequestConfig,
     type UnifiedFont,
     appliedFontsManager,
+    fontStore,
 } from '../../model';
-import { fontStore } from '../../model/store';
 
 interface Props extends
     Omit<
@@ -53,30 +53,42 @@ const isLoading = $derived(
     fontStore.isFetching || fontStore.isLoading,
 );
 
-function handleInternalVisibleChange(visibleItems: UnifiedFont[]) {
+let visibleFonts = $state<UnifiedFont[]>([]);
-    const configs: FontLoadRequestConfig[] = [];
-
-    visibleItems.forEach(item => {
-        const url = getFontUrl(item, weight);
-
-        if (url) {
-            configs.push({
-                id: item.id,
-                name: item.name,
-                weight,
-                url,
-                isVariable: item.features?.isVariable,
-            });
-        }
-    });
-
-    // Auto-register fonts with the manager
-    appliedFontsManager.touch(configs);
 
+function handleInternalVisibleChange(items: UnifiedFont[]) {
+    visibleFonts = items;
     // Forward the call to any external listener
-    // onVisibleItemsChange?.(visibleItems);
+    onVisibleItemsChange?.(items);
 }
 
+// Re-touch whenever visible set or weight changes — fixes weight-change gap
+$effect(() => {
+    const configs: FontLoadRequestConfig[] = visibleFonts.flatMap(item => {
+        const url = getFontUrl(item, weight);
+        if (!url) return [];
+        return [{ id: item.id, name: item.name, weight, url, isVariable: item.features?.isVariable }];
+    });
+    if (configs.length > 0) {
+        appliedFontsManager.touch(configs);
+    }
+});
+
+// Pin visible fonts so the eviction policy never removes on-screen entries.
+// Cleanup captures the snapshot values, so a weight change unpins the old
+// weight before pinning the new one.
+$effect(() => {
+    const w = weight;
+    const fonts = visibleFonts;
+    for (const f of fonts) {
+        appliedFontsManager.pin(f.id, w, f.features?.isVariable);
+    }
+    return () => {
+        for (const f of fonts) {
+            appliedFontsManager.unpin(f.id, w, f.features?.isVariable);
+        }
+    };
+});
+
 /**
  * Load more fonts by moving to the next page
  */