Replace accent presets with the sunset-to-sea family

Swap Toffee/Slate/Evergreen/Lavender for rose/coral/amber/teal — four ramps
sharing one lightness/saturation curve (src/renderer/src/theme.ts). Default
accent is now teal. Updates ACCENT_COLORS (src/shared/ipc.ts), the settings
default + stale-value coercion (src/main/settings.ts), the dev/store fallbacks
(main.tsx, store/settings.ts), and the native window background to match the
new pageBackground.light (src/main/index.ts).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main/index.ts

@@ -63,7 +63,7 @@ let mainWindow: BrowserWindow | null = null
 // src/renderer/src/theme.ts. Set as the window's NATIVE background so the
 // one-frame compositor repaint (when a tooltip/dropdown overlay first paints on
 // Windows) shows the app's current color instead of a mismatched white flash.
-const THEME_BACKGROUND = { light: '#f6f1ef', dark: '#161618' } as const
+const THEME_BACKGROUND = { light: '#f7f7f8', dark: '#161618' } as const
 
 // 'system' isn't a real background — resolve it against the OS's current
 // preference (nativeTheme.themeSource defaults to 'system', so this tracks it

src/main/settings.ts

@@ -23,7 +23,7 @@ const DEFAULTS: Settings = {
   maxConcurrent: 2,
   filenameTemplate: '%(title)s.%(ext)s',
   theme: 'light',
-  accentColor: 'toffee',
+  accentColor: 'teal',
   clipboardWatch: true,
   downloadOptions: DEFAULT_DOWNLOAD_OPTIONS,
   proxy: '',
@@ -106,6 +106,11 @@ export function getSettings(): Settings {
   if (!downloadOptionsEqual(sanitized, cur.downloadOptions)) {
     s.set('downloadOptions', sanitized)
   }
+  // Coerce an accentColor left over from a renamed/removed preset (e.g. an old
+  // 'toffee' or 'indigo' default) onto the current default, so it resolves cleanly.
+  if (!(ACCENT_COLORS as readonly string[]).includes(cur.accentColor)) {
+    s.set('accentColor', DEFAULTS.accentColor)
+  }
   return s.store
 }