Share previews: Open Graph and Twitter tags, a share card and a touch icon

The tags live in app.html because link scrapers do not run the client,
and the card and icon are rendered from the site's own palette and the
Spellcast snap silhouette.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/app.html

@@ -4,6 +4,24 @@
 		<meta charset="utf-8" />
 		<meta name="viewport" content="width=device-width, initial-scale=1" />
 		<meta name="color-scheme" content="dark" />
+		<meta name="theme-color" content="#121a20" />
+		<title>Waving Hands</title>
+		<meta name="description" content="A duel of gestures against a rival wizard, after Richard Bartle's 1977 pencil-and-paper game. Free to play in the browser." />
+		<link rel="canonical" href="https://hands.kestrelsnest.social/" />
+		<link rel="apple-touch-icon" href="/apple-touch-icon.png" />
+		<meta property="og:type" content="website" />
+		<meta property="og:site_name" content="Waving Hands" />
+		<meta property="og:title" content="Waving Hands" />
+		<meta property="og:description" content="A duel of gestures against a rival wizard, after Richard Bartle's 1977 pencil-and-paper game. Free to play in the browser." />
+		<meta property="og:url" content="https://hands.kestrelsnest.social/" />
+		<meta property="og:image" content="https://hands.kestrelsnest.social/og.png" />
+		<meta property="og:image:width" content="1200" />
+		<meta property="og:image:height" content="630" />
+		<meta property="og:image:alt" content="Waving Hands: a ledger of gesture letters beside the title and a snapping hand." />
+		<meta name="twitter:card" content="summary_large_image" />
+		<meta name="twitter:title" content="Waving Hands" />
+		<meta name="twitter:description" content="A duel of gestures against a rival wizard, after Richard Bartle's 1977 pencil-and-paper game. Free to play in the browser." />
+		<meta name="twitter:image" content="https://hands.kestrelsnest.social/og.png" />
 		<link rel="preconnect" href="https://fonts.googleapis.com" />
 		<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
 		<link

src/routes/+page.svelte

@@ -40,7 +40,6 @@
 
 <svelte:head>
 	<title>Waving Hands</title>
-	<meta name="description" content="A duel of gestures against a rival wizard, after Richard Bartle's 1977 pencil-and-paper game." />
 </svelte:head>
 
 <header class="masthead">