refactor(GetFonts): unify filterManager factory + singleton under model/state

Merge the factory previously in lib/filterManager/ with the singleton
previously in model/state/manager.svelte.ts into a single
model/state/filterManager/ slice. The factory builds stateful runes-backed
objects, so it belongs alongside the singleton in model/, not in lib/.

lib/ now contains only the pure mapManagerToParams transform.
Public barrel signature unchanged.

src/features/GetFonts/index.ts

@@ -1,19 +1,25 @@
+export { mapManagerToParams } from './lib';
+
 export {
+    /**
+     * Filter Manager
+     */
     createFilterManager,
     type FilterManager,
-    mapManagerToParams,
-} from './lib';
-
-export { filtersStore } from './model/state/filters.svelte';
-export { filterManager } from './model/state/manager.svelte';
-
-export {
+    filterManager,
+    /**
+     * Filter Store
+     */
+    filtersStore,
+    /**
+     * Sort Store
+     */
     SORT_MAP,
     SORT_OPTIONS,
     type SortApiValue,
     type SortOption,
     sortStore,
-} from './model/store/sortStore.svelte';
+} from './model';
 
 export {
     FilterControls,

src/features/GetFonts/lib/index.ts

@@ -1,6 +1 @@
-export {
-    createFilterManager,
-    type FilterManager,
-} from './filterManager/filterManager.svelte';
-
 export { mapManagerToParams } from './mapper/mapManagerToParams';

src/features/GetFonts/lib/mapper/mapManagerToParams.ts

@@ -1,5 +1,5 @@
 import type { ProxyFontsParams } from '$entities/Font/api';
-import type { FilterManager } from '../filterManager/filterManager.svelte';
+import type { FilterManager } from '../../model';
 
 /**
  * Maps filter manager to proxy API parameters.

src/features/GetFonts/model/index.ts

@@ -23,11 +23,19 @@ export {
  * Main filter controller
  */
 export {
+    /**
+     * Factory for constructing a filter manager instance
+     */
+    createFilterManager,
+    /**
+     * Reactive interface returned by `createFilterManager`
+     */
+    type FilterManager,
     /**
      * High-level manager for syncing search and filters
      */
     filterManager,
-} from './state/manager.svelte';
+} from './state/filterManager/filterManager.svelte';
 
 /**
  * Side-effect import: installs the global filterManager+sortStore → fontStore

src/features/GetFonts/model/state/bindings.svelte.ts

@@ -13,8 +13,8 @@ import { fontStore } from '$entities/Font';
 import { untrack } from 'svelte';
 import { mapManagerToParams } from '../../lib/mapper/mapManagerToParams';
 import { sortStore } from '../store/sortStore.svelte';
+import { filterManager } from './filterManager/filterManager.svelte';
 import { filtersStore } from './filters.svelte';
-import { filterManager } from './manager.svelte';
 
 $effect.root(() => {
     /**

src/features/GetFonts/model/state/filterManager/filterManager.svelte.ts

@@ -1,9 +1,12 @@
 /**
- * Filter manager for font filtering
+ * Filter manager factory and singleton.
  *
- * Manages multiple filter groups (providers, categories, subsets)
- * with debounced search input. Provides reactive state for filter
- * selections and convenience methods for bulk operations.
+ * Owns multiple filter groups (providers, categories, subsets) plus a
+ * debounced search input. Provides reactive state for filter selections
+ * and convenience methods for bulk operations.
+ *
+ * The factory (`createFilterManager`) is exported for tests; the app
+ * consumes the `filterManager` singleton at the bottom of this file.
  *
  * @example
  * ```ts
@@ -25,7 +28,7 @@ import { createDebouncedState } from '$shared/lib/helpers';
 import type {
     FilterConfig,
     FilterGroupConfig,
-} from '../../model';
+} from '../../types/filter';
 
 /**
  * Creates a filter manager instance
@@ -123,3 +126,15 @@ export function createFilterManager<TValue extends string>(config: FilterConfig<
 }
 
 export type FilterManager = ReturnType<typeof createFilterManager>;
+
+/**
+ * App-wide filter manager singleton.
+ *
+ * Constructed with empty groups; the filtersStore → filterManager wiring
+ * lives in `./bindings.svelte` and populates groups once backend filter
+ * metadata arrives.
+ */
+export const filterManager = createFilterManager({
+    queryValue: '',
+    groups: [],
+});

src/features/GetFonts/model/state/manager.svelte.ts

@@ -1,14 +0,0 @@
-/**
- * Filter manager singleton.
- *
- * Constructed with empty groups; the filtersStore → filterManager wiring
- * lives in `./bindings.svelte` and populates groups once the backend
- * filter metadata arrives.
- */
-
-import { createFilterManager } from '../../lib/filterManager/filterManager.svelte';
-
-export const filterManager = createFilterManager({
-    queryValue: '',
-    groups: [],
-});