refactor: simplify TOML common config handling by removing markers

- Remove COMMON_CONFIG_MARKER_START/END constants
- Simplify config snippet addition/removal logic
- Use natural append/replace approach instead of markers
- Fix unused variable warning
- Improve user experience with cleaner config output

src/components/AppSwitcher.tsx

@@ -26,8 +26,8 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
         <ClaudeIcon
           size={16}
           className={
-            activeApp === "claude" 
-              ? "text-[#D97757] dark:text-[#D97757] transition-colors duration-200" 
+            activeApp === "claude"
+              ? "text-[#D97757] dark:text-[#D97757] transition-colors duration-200"
               : "text-gray-500 dark:text-gray-400 group-hover:text-[#D97757] dark:group-hover:text-[#D97757] transition-colors duration-200"
           }
         />