refactor(entities/Font): relocate FontSampler from DisplayFont, invert typography

DisplayFont was not a feature (FSD+ A-6): the whole slice was one
presentational component that renders a Font styled by typography, with no
model/domain/action. To get typography it reached sideways into a sibling
feature (`$features/AdjustTypography/model`) — a feature->feature edge
(C-1), the symptom of the mislayering, not the disease.

Fix by inversion, mirroring the existing `status` prop pattern:

- move FontSampler into entities/Font/ui (it now uses only entity siblings
  + $shared/ui)
- it accepts a `typography` prop typed to a minimal contract defined in the
  component; the AdjustTypography store satisfies it structurally, so the
  entity has no dependency on the feature
- SampleList (owns both) injects its typographySettingsStore as the prop
- delete the DisplayFont slice; export FontSampler from the Font barrel;
  relocate the story (now passes a mock typography)

Resolves A-6, A-7, and the FontSampler half of C-1. Verified: 0 type
errors, 0 lint (boundary rule satisfied), 905 unit + 213 component tests,
production build OK.

src/entities/Font/ui/FontSampler/FontSampler.stories.svelte

@@ -0,0 +1,133 @@
+<script module>
+import Providers from '$shared/lib/storybook/Providers.svelte';
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import FontSampler from './FontSampler.svelte';
+
+const { Story } = defineMeta({
+    title: 'Entities/Font/FontSampler',
+    component: FontSampler,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Displays a sample text with a given font in a contenteditable element. Visual design matches FontCard: sharp corners, brand hover accent, header stats showing font properties (size, weight, line height, letter spacing). Staggered entrance animation based on index.',
+            },
+            story: { inline: false },
+        },
+    },
+    argTypes: {
+        font: {
+            control: 'object',
+            description: 'Font information object',
+        },
+        status: {
+            control: 'select',
+            options: ['loading', 'loaded', 'error'],
+            description: 'Font-load status, supplied by the composing widget and forwarded to FontApplicator',
+        },
+        text: {
+            control: 'text',
+            description: 'Editable sample text (two-way bindable)',
+        },
+        index: {
+            control: { type: 'number', min: 0 },
+            description: 'Position index — drives the staggered entrance delay',
+        },
+    },
+});
+</script>
+
+<script lang="ts">
+import type { ComponentProps } from 'svelte';
+import type { UnifiedFont } from '../../model/types';
+
+// Mock fonts for testing
+const mockArial: UnifiedFont = {
+    id: 'arial',
+    name: 'Arial',
+    provider: 'google',
+    category: 'sans-serif',
+    subsets: ['latin'],
+    variants: ['400', '700'],
+    styles: {
+        regular: '',
+        bold: '',
+    },
+    metadata: {
+        cachedAt: Date.now(),
+        version: '1.0',
+        popularity: 1,
+    },
+    features: {
+        isVariable: false,
+    },
+};
+
+const mockGeorgia: UnifiedFont = {
+    id: 'georgia',
+    name: 'Georgia',
+    provider: 'google',
+    category: 'serif',
+    subsets: ['latin'],
+    variants: ['400', '700'],
+    styles: {
+        regular: '',
+        bold: '',
+    },
+    metadata: {
+        cachedAt: Date.now(),
+        version: '1.0',
+        popularity: 2,
+    },
+    features: {
+        isVariable: false,
+    },
+};
+
+// Stand-in for the AdjustTypography store the composing widget injects.
+const mockTypography = {
+    renderedSize: 48,
+    weight: 400,
+    height: 1.5,
+    spacing: 0,
+};
+</script>
+
+<Story
+    name="Default"
+    args={{
+        font: mockArial,
+        status: 'loaded',
+        text: 'The quick brown fox jumps over the lazy dog',
+        index: 0,
+        typography: mockTypography,
+    }}
+>
+    {#snippet template(args: ComponentProps<typeof FontSampler>)}
+        <Providers>
+            <div class="max-w-2xl mx-auto">
+                <FontSampler {...args} />
+            </div>
+        </Providers>
+    {/snippet}
+</Story>
+<Story
+    name="Long Text"
+    args={{
+        font: mockGeorgia,
+        status: 'loaded',
+        text:
+            'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.',
+        index: 1,
+        typography: mockTypography,
+    }}
+>
+    {#snippet template(args: ComponentProps<typeof FontSampler>)}
+        <Providers>
+            <div class="max-w-2xl mx-auto">
+                <FontSampler {...args} />
+            </div>
+        </Providers>
+    {/snippet}
+</Story>