refactor(features): rename SetupFont to AdjustTypography + reorganize

Structural:
- Merge factory + singleton from lib/settingsManager and model/state into
  one model/store/typographySettingsStore/ slice
- Drop now-empty lib/ and model/state/ directories

Semantic:
- Rename feature SetupFont -> AdjustTypography (the feature owns
  continuous typography adjustment, not one-time font setup)
- Drop "Manager" from TypographySettingsManager -> TypographySettingsStore
  (class + factory); singleton typographySettingsStore unchanged

All consumers (Character, Line, SampleList, SliderArea, FontSampler,
comparisonStore) updated. Public barrel signature changed: now exports
createTypographySettingsStore and type TypographySettingsStore.

src/widgets/ComparisonView/ui/Line/Line.svelte

@@ -3,7 +3,7 @@
     Renders a line of text in the SliderArea
 -->
 <script lang="ts">
-import { typographySettingsStore } from '$features/SetupFont';
+import { typographySettingsStore } from '$features/AdjustTypography';
 import type { Snippet } from 'svelte';
 
 interface LineChar {