feat(Board): add CandidateCard mini switcher

src/widgets/Board/ui/CandidateCard/CandidateCard.stories.svelte

@@ -0,0 +1,36 @@
+<script module>
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import CandidateCard from './CandidateCard.svelte';
+
+const { Story } = defineMeta({
+    title: 'Widgets/Board/CandidateCard',
+    component: CandidateCard,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Compact rail switcher for one pairing: the two font names in their own fonts. Click makes the pairing focal (aria-current). Not an evaluation surface — no real-length specimen.',
+            },
+            story: { inline: false },
+        },
+    },
+});
+</script>
+
+<script lang="ts">
+import type { ComponentProps } from 'svelte';
+</script>
+
+<Story
+    name="Default"
+    args={{
+        pairing: { id: 'demo-1', headerFontId: 'Playfair Display', bodyFontId: 'Source Sans Pro' },
+    }}
+>
+    {#snippet template(args: ComponentProps<typeof CandidateCard>)}
+        <div style="max-width: 220px;">
+            <CandidateCard {...args} />
+        </div>
+    {/snippet}
+</Story>

src/widgets/Board/ui/CandidateCard/CandidateCard.svelte

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+<!--
+    Component: CandidateCard
+    Compact switcher for one pairing in the rail — NOT an evaluation surface. Shows
+    the two font names rendered in their own fonts at a small decorative size
+    (clamp/cqi is fine here: chrome, not the honest-measure specimen). Click makes
+    the pairing focal. Container-query driven so the same card works anywhere.
+-->
+<script lang="ts">
+import {
+    FontApplicator,
+    type UnifiedFont,
+    getFontLifecycleManager,
+} from '$entities/Font';
+import type {
+    Pairing,
+    Role,
+} from '$entities/Pairing';
+import { getBoard } from '$features/CompareBoard';
+
+interface Props {
+    /**
+     * The pairing this card switches to.
+     */
+    pairing: Pairing;
+}
+
+let { pairing }: Props = $props();
+
+const board = getBoard();
+const lifecycle = getFontLifecycleManager();
+
+const isFocal = $derived(board.focalId === pairing.id);
+const fonts = $derived(board.resolvePairingFonts(pairing));
+</script>
+
+<button
+    type="button"
+    class="
+        @container flex w-full flex-col gap-1 rounded-lg border p-3 text-left transition-colors
+        aria-current:border-indigo-500 aria-current:bg-indigo-50
+        border-slate-200 hover:border-slate-300
+    "
+    aria-current={isFocal ? 'true' : undefined}
+    onclick={() => board.setFocal(pairing.id)}
+>
+    {@render name('header', fonts.header?.name ?? pairing.headerFontId, fonts.header)}
+    {@render name('body', fonts.body?.name ?? pairing.bodyFontId, fonts.body)}
+</button>
+
+{#snippet name(role: Role, label: string, font: UnifiedFont | undefined)}
+    {@const size = role === 'header' ? 'clamp(0.9rem, 5cqi, 1.25rem)' : 'clamp(0.75rem, 4cqi, 1rem)'}
+    {#if font}
+        <FontApplicator
+            {font}
+            status={lifecycle.getFontStatus(font.id, board.typo[role].weight, font.features?.isVariable)}
+        >
+            <span class="block truncate" style:font-size={size}>{label}</span>
+        </FontApplicator>
+    {:else}
+        <span class="block truncate text-slate-500" style:font-size={size}>{label}</span>
+    {/if}
+{/snippet}