feat: add theme selector with multiple dark themes

Add theme dropdown in settings with Light, Dark, System plus
Zinc, Midnight, Claude, and Ghostty dark variants. Each theme
has its own accent color and surface tints. Desaturate terminal
ANSI colors across all dark themes. Add surfaceSidebarHover
semantic token so hover states go the right direction in both
light and dark modes. Self-heal if a stored theme no longer exists.

packages/app/src/hooks/use-settings.ts

@@ -6,10 +6,14 @@ export const APP_SETTINGS_KEY = "@paseo:app-settings";
 const LEGACY_SETTINGS_KEY = "@paseo:settings";
 const APP_SETTINGS_QUERY_KEY = ["app-settings"];
 
+import { THEME_TO_UNISTYLES, type ThemeName } from "@/styles/theme";
+
 export type SendBehavior = "interrupt" | "queue";
 
+const VALID_THEMES = new Set<string>([...Object.keys(THEME_TO_UNISTYLES), "auto"]);
+
 export interface AppSettings {
-  theme: "dark" | "light" | "auto";
+  theme: ThemeName | "auto";
   manageBuiltInDaemon: boolean;
   sendBehavior: SendBehavior;
 }
@@ -78,6 +82,9 @@ export async function loadSettingsFromStorage(): Promise<AppSettings> {
     const stored = await AsyncStorage.getItem(APP_SETTINGS_KEY);
     if (stored) {
       const parsed = JSON.parse(stored) as Partial<AppSettings>;
+      if (parsed.theme && !VALID_THEMES.has(parsed.theme)) {
+        parsed.theme = DEFAULT_APP_SETTINGS.theme;
+      }
       return { ...DEFAULT_APP_SETTINGS, ...parsed };
     }