feat(ui): paint VK status bar to the app theme (VKWebAppSetViewSettings)

Parity with the Telegram chrome painting: on a VK Mini App launch and on
every theme change, set VK's status-bar appearance (and, on Android, the
action/navigation bar colours) from the app's live theme tokens, so the VK
chrome matches the UI instead of clashing.

syncVKChrome mirrors syncTelegramChrome; the status-bar appearance is
derived from the --bg token's luminance (appearanceForBg, unit-tested).
Wired into the VK onScheme handler (fires on launch + on theme change) and
setTheme. Docs: UI_DESIGN VK integration.

ui/src/lib/app.svelte.ts

@@ -31,7 +31,7 @@ import {
   telegramCloudGet,
   telegramCloudSet,
 } from './telegram';
-import { onVKPath, insideVK, vkInit, vkDisableSwipeBack, vkLaunchParams, vkUserName, vkStartParam, vkOnScheme, vkOnInsets } from './vk';
+import { onVKPath, insideVK, vkInit, vkDisableSwipeBack, vkLaunchParams, vkUserName, vkStartParam, vkOnScheme, vkOnInsets, vkSetViewSettings, appearanceForBg } from './vk';
 import { haptic } from './haptics';
 import { CLOUD_PREFS_KEY, decodeClientPrefs, encodeClientPrefs } from './cloudprefs';
 import { parseStartParam } from './deeplink';
@@ -552,6 +552,19 @@ function syncTelegramChrome(): void {
   );
 }
 
+/**
+ * syncVKChrome paints VK's status bar (and, on Android, the action/navigation bars) from the app's
+ * live theme tokens, so the surrounding VK chrome matches the UI. A no-op outside VK. Parity with
+ * syncTelegramChrome.
+ */
+function syncVKChrome(): void {
+  if (!insideVK() || typeof document === 'undefined') return;
+  const cs = getComputedStyle(document.documentElement);
+  const bg = cs.getPropertyValue('--bg').trim();
+  const bgElev = cs.getPropertyValue('--bg-elev').trim();
+  void vkSetViewSettings(appearanceForBg(bg), bgElev, bg);
+}
+
 /**
  * syncTelegramSafeArea mirrors Telegram's safe-area insets into CSS vars: the content-safe-area top
  * (the height Telegram's native nav overlays the viewport in fullscreen) into --tg-content-top
@@ -694,6 +707,9 @@ export async function bootstrap(): Promise<void> {
     // VK mobile webview's prefers-color-scheme does not track it).
     void vkOnScheme((scheme) => {
       if (app.theme === 'auto') applyTheme(scheme);
+      // Repaint VK's status/nav bars to the resolved theme; this handler also fires on launch, so it
+      // covers the initial paint (auto → the VK scheme just applied, explicit → the theme from boot).
+      syncVKChrome();
     });
     // Clear the device safe area from VK's insets — the VK mobile webview does not surface them via
     // CSS env() (notably the Android home bar). max() keeps whichever of env() / the VK value is real.
@@ -995,6 +1011,7 @@ async function reconcileCloudPrefs(): Promise<void> {
 export function setTheme(theme: ThemePref): void {
   app.theme = theme;
   applyTheme(theme);
+  syncVKChrome();
   persistPrefs();
 }
 

ui/src/lib/vk.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { insideVK, onVKPath, vkAppId, vkLaunchParams, vkStartParam } from './vk';
+import { insideVK, onVKPath, vkAppId, vkLaunchParams, vkStartParam, appearanceForBg } from './vk';
 
 describe('vk launch detection', () => {
   afterEach(() => vi.unstubAllGlobals());
@@ -49,3 +49,25 @@ describe('vk launch params', () => {
     expect(vkStartParam()).toBe('');
   });
 });
+
+describe('appearanceForBg', () => {
+  it('maps a dark background to the dark appearance (light status-bar icons)', () => {
+    expect(appearanceForBg('#0f1115')).toBe('dark');
+    expect(appearanceForBg('#171a21')).toBe('dark');
+  });
+
+  it('maps a light background to the light appearance (dark status-bar icons)', () => {
+    expect(appearanceForBg('#f3f4f6')).toBe('light');
+    expect(appearanceForBg('#ffffff')).toBe('light');
+  });
+
+  it('accepts shorthand hex and surrounding whitespace (a raw CSS custom-property value)', () => {
+    expect(appearanceForBg('#000')).toBe('dark');
+    expect(appearanceForBg('  #fff  ')).toBe('light');
+  });
+
+  it('defaults to light for an unparseable colour', () => {
+    expect(appearanceForBg('')).toBe('light');
+    expect(appearanceForBg('rgb(0, 0, 0)')).toBe('light');
+  });
+});

ui/src/lib/vk.ts

@@ -198,3 +198,42 @@ export async function vkDisableSwipeBack(): Promise<void> {
     // Outside VK / unsupported: VK's default gesture handling stays as-is.
   }
 }
+
+/**
+ * appearanceForBg maps a background colour to the VK view appearance: a dark background wants the
+ * 'dark' appearance (light status-bar icons), a light one 'light'. It accepts a `#rgb` / `#rrggbb`
+ * string (the app's `--bg` token); anything unparseable defaults to 'light'. Pure, so it is
+ * unit-tested.
+ */
+export function appearanceForBg(bg: string): 'light' | 'dark' {
+  const hex = bg.trim().replace(/^#/, '');
+  const full = hex.length === 3 ? [...hex].map((c) => c + c).join('') : hex;
+  if (full.length !== 6 || /[^0-9a-fA-F]/.test(full)) return 'light';
+  const r = parseInt(full.slice(0, 2), 16);
+  const g = parseInt(full.slice(2, 4), 16);
+  const b = parseInt(full.slice(4, 6), 16);
+  // Rec. 601 luma; below the midpoint is a dark background.
+  return 0.299 * r + 0.587 * g + 0.114 * b < 128 ? 'dark' : 'light';
+}
+
+/**
+ * vkSetViewSettings paints VK's status bar — and, on Android, the action and navigation bars — to
+ * match the app. appearance is the VK status-bar appearance ('light' | 'dark'); actionBarColor and
+ * navigationBarColor are Android-only hex colours (ignored elsewhere). Best-effort; a no-op outside
+ * VK or on a client without the method.
+ */
+export async function vkSetViewSettings(
+  appearance: 'light' | 'dark',
+  actionBarColor: string,
+  navigationBarColor: string,
+): Promise<void> {
+  try {
+    await (await bridge()).send('VKWebAppSetViewSettings', {
+      status_bar_style: appearance,
+      action_bar_color: actionBarColor,
+      navigation_bar_color: navigationBarColor,
+    });
+  } catch {
+    // Outside VK / unsupported: the client keeps its default bars.
+  }
+}