fix: restore @ts-expect-error for browser_style in options_ui

Lost when refactoring open_in_tab into a conditional spread for Safari.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: rxliuli

packages/wxt/src/core/utils/manifest.ts

@@ -336,6 +336,7 @@ function addEntrypoints(
       ...(wxt.config.browser !== 'safari' && {
         open_in_tab: options.options.openInTab ?? false,
       }),
+      // @ts-expect-error: Not typed by @wxt-dev/browser, but supported by Firefox
       browser_style:
         wxt.config.browser === 'firefox'
           ? options.options.browserStyle