feat(web/m7-363): theme-color meta follows resolved theme

web/src/lib/theme/__test__/Probe.svelte

@@ -0,0 +1,4 @@
+<script lang="ts">
+	import { applyMetaThemeColor } from '../applyMetaThemeColor.svelte';
+	applyMetaThemeColor();
+</script>

web/src/lib/theme/applyMetaThemeColor.svelte.test.ts

@@ -0,0 +1,50 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { render } from '@testing-library/svelte';
+import { setTheme } from '$lib/stores/theme.svelte';
+import Probe from './__test__/Probe.svelte';
+
+describe('applyMetaThemeColor', () => {
+	beforeEach(() => {
+		document.head.innerHTML = '';
+	});
+
+	afterEach(() => {
+		document.head.innerHTML = '';
+		// Reset to a known baseline; setTheme persists to localStorage,
+		// but each test starts with head cleared anyway.
+		setTheme('dark');
+	});
+
+	it('creates a meta[name="theme-color"]:not([media]) on mount with the dark hex', () => {
+		setTheme('dark');
+		render(Probe);
+		const meta = document.querySelector<HTMLMetaElement>(
+			'meta[name="theme-color"]:not([media])'
+		);
+		expect(meta).not.toBeNull();
+		expect(meta!.content).toBe('#14171A');
+	});
+
+	it('updates the meta content when the resolved theme flips to light', async () => {
+		setTheme('dark');
+		render(Probe);
+		setTheme('light');
+		await Promise.resolve();
+		const meta = document.querySelector<HTMLMetaElement>(
+			'meta[name="theme-color"]:not([media])'
+		);
+		expect(meta).not.toBeNull();
+		expect(meta!.content).toBe('#F8F5EE');
+	});
+
+	it('reuses an existing meta tag instead of stacking duplicates', async () => {
+		setTheme('dark');
+		render(Probe);
+		setTheme('light');
+		await Promise.resolve();
+		setTheme('dark');
+		await Promise.resolve();
+		const metas = document.querySelectorAll('meta[name="theme-color"]:not([media])');
+		expect(metas.length).toBe(1);
+	});
+});

web/src/lib/theme/applyMetaThemeColor.svelte.ts

@@ -0,0 +1,28 @@
+import { resolvedTheme } from '$lib/stores/theme.svelte';
+
+const DARK = '#14171A';
+const LIGHT = '#F8F5EE';
+
+// applyMetaThemeColor wires a Svelte 5 $effect that keeps a single
+// <meta name="theme-color"> (without a media query) in sync with the
+// resolved theme. The Vite build plugin injects two media-query
+// variants for first paint / pre-hydration; the meta tag this helper
+// manages is added on hydration and tracks the user's explicit
+// Dark / Light / System choice. On a phone, the mobile address bar
+// retints the moment the user changes the theme in Settings.
+//
+// Must be called from a component setup (uses $effect).
+export function applyMetaThemeColor(): void {
+	$effect(() => {
+		const target = resolvedTheme.value === 'light' ? LIGHT : DARK;
+		let meta = document.querySelector<HTMLMetaElement>(
+			'meta[name="theme-color"]:not([media])'
+		);
+		if (!meta) {
+			meta = document.createElement('meta');
+			meta.name = 'theme-color';
+			document.head.appendChild(meta);
+		}
+		meta.content = target;
+	});
+}

web/src/routes/+layout.svelte

@@ -15,6 +15,7 @@
   } from '$lib/player/store.svelte';
   import { useMediaSession } from '$lib/player/mediaSession.svelte';
   import { useEventsDispatcher } from '$lib/player/events.svelte';
+  import { applyMetaThemeColor } from '$lib/theme/applyMetaThemeColor.svelte';
 
   let { children } = $props<{ children: import('svelte').Snippet }>();
   let audioEl: HTMLAudioElement | undefined = $state();
@@ -66,6 +67,7 @@
 
   useMediaSession();
   useEventsDispatcher();
+  applyMetaThemeColor();
 </script>
 
 <audio