The guide and the rules page keep the room they were opened from, and carry it to each other and back

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jm2auWk6RP71CjaAb4FMoG

template/src/routes/rules/+page.svelte

@@ -6,6 +6,7 @@
 
 	/** Opened from a table, the page offers the way back to it. */
 	const room = $derived((page.url.searchParams.get('room') ?? '').toUpperCase());
+	const withRoom = $derived((path: string) => (room ? `${path}?room=${room}` : path));
 </script>
 
 <svelte:head>
@@ -14,7 +15,7 @@
 
 <main class="rules">
 	<header>
-		{#if room}<a class="back" href={`/join/${room}`}>Back to your game</a> · {/if}<a class="back" href="/">Back to the hall</a> · <a class="back" href="/guide">How to play</a>
+		{#if room}<a class="back" href={`/join/${room}`}>Back to your game</a> · {/if}<a class="back" href="/">Back to the hall</a> · <a class="back" href={withRoom('/guide')}>How to play</a>
 		<h1>The rules</h1>
 		<p class="lede">One paragraph on where these rules come from and which edition or text this page follows.</p>
 	</header>