Make sponsor bios collapsible with Read bio toggle

- Bios hidden by default
- Click/tap "Read bio" to expand
- Click "Hide bio" to collapse
- Chevron animates to indicate state

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: Matt

src/lib/components/SponsorCard.svelte

@@ -13,6 +13,11 @@
 	}
 
 	let { sponsor }: Props = $props();
+	let expanded = $state(false);
+
+	function toggleBio() {
+		expanded = !expanded;
+	}
 </script>
 
 <article class="sponsor-card sponsor-card--{sponsor.tier}">
@@ -31,7 +36,31 @@
 			<span class="sponsor-tier">{sponsor.tier}</span>
 		</div>
 
-		<p class="sponsor-bio">{sponsor.bio}</p>
+		{#if sponsor.bio}
+			<button
+				class="bio-toggle"
+				onclick={toggleBio}
+				aria-expanded={expanded}
+				aria-controls="bio-{sponsor.id}"
+			>
+				{expanded ? 'Hide bio' : 'Read bio'}
+				<svg
+					class="chevron"
+					class:rotated={expanded}
+					width="16"
+					height="16"
+					viewBox="0 0 16 16"
+					fill="none"
+					aria-hidden="true"
+				>
+					<path d="M4 6L8 10L12 6" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+				</svg>
+			</button>
+
+			{#if expanded}
+				<p id="bio-{sponsor.id}" class="sponsor-bio">{sponsor.bio}</p>
+			{/if}
+		{/if}
 
 		<a
 			href={sponsor.website}
@@ -128,12 +157,37 @@
 		color: var(--color-text-light);
 	}
 
+	.bio-toggle {
+		display: flex;
+		align-items: center;
+		gap: var(--space-xs);
+		padding: var(--space-xs) 0;
+		color: var(--color-primary);
+		font-size: var(--text-sm);
+		font-weight: 500;
+		margin-bottom: var(--space-sm);
+	}
+
+	.bio-toggle:hover,
+	.bio-toggle:focus-visible {
+		text-decoration: underline;
+	}
+
+	.chevron {
+		transition: transform var(--transition-fast);
+	}
+
+	.chevron.rotated {
+		transform: rotate(180deg);
+	}
+
 	.sponsor-bio {
-		flex: 1;
 		font-size: var(--text-sm);
 		line-height: 1.6;
 		color: var(--color-gray-600);
 		margin-bottom: var(--space-md);
+		padding-top: var(--space-sm);
+		border-top: 1px solid var(--color-gray-200);
 	}
 
 	.sponsor-link {