feat(landing): adopt Space Grotesk as display font

Replace Syne with Space Grotesk across the marketing landing page to match the unified ACT brand (technical grotesque that pairs with the DM Mono wordmark). Drops display heading weights 800 -> 700, Space Grotesk's ceiling.

Author: GamePad64

src/layouts/Landing.astro

@@ -18,7 +18,7 @@ const { title, description } = Astro.props;
 		<link rel="preconnect" href="https://fonts.googleapis.com" />
 		<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
 		<link
-			href="https://fonts.googleapis.com/css2?family=DM+Mono:ital,wght@0,400;0,500;1,400&family=Syne:wght@400;600;700;800&family=Instrument+Sans:ital,wght@0,400;0,500;0,600;0,700;1,400&display=swap"
+			href="https://fonts.googleapis.com/css2?family=DM+Mono:ital,wght@0,400;0,500;1,400&family=Space+Grotesk:wght@400;500;600;700&family=Instrument+Sans:ital,wght@0,400;0,500;0,600;0,700;1,400&display=swap"
 			rel="stylesheet"
 		/>
 	</head>
@@ -62,7 +62,7 @@ const { title, description } = Astro.props;
 		--text-secondary: #9898aa;
 		--text-muted: #5c5c72;
 
-		--font-display: 'Syne', sans-serif;
+		--font-display: 'Space Grotesk', sans-serif;
 		--font-body: 'Instrument Sans', sans-serif;
 		--font-mono: 'DM Mono', monospace;
 	}

src/pages/index.astro

@@ -427,7 +427,7 @@ $ act run ghcr.io/me/my-tool:1.0 <span class="flag">--mcp</span> <span class="fl
 	.hero-title {
 		font-family: var(--font-display);
 		font-size: clamp(3rem, 8vw, 6rem);
-		font-weight: 800;
+		font-weight: 700;
 		line-height: 1.05;
 		letter-spacing: -0.03em;
 		margin-bottom: 1.5rem;
@@ -713,7 +713,7 @@ $ act run ghcr.io/me/my-tool:1.0 <span class="flag">--mcp</span> <span class="fl
 	.section-title {
 		font-family: var(--font-display);
 		font-size: 2.5rem;
-		font-weight: 800;
+		font-weight: 700;
 		letter-spacing: -0.03em;
 		margin-bottom: 3rem;
 		text-align: center;
@@ -855,7 +855,7 @@ $ act run ghcr.io/me/my-tool:1.0 <span class="flag">--mcp</span> <span class="fl
 	.cta-card h2 {
 		font-family: var(--font-display);
 		font-size: 2rem;
-		font-weight: 800;
+		font-weight: 700;
 		margin-bottom: 0.5rem;
 		letter-spacing: -0.02em;
 	}