Codex app

# Codex app ### New features - Added command-menu file search, including `Cmd+P` routing into workspace file search. - Added rich previews in the sidebar file viewer for images, PDFs, and Markdown. - Added terminal tabs per thread, a selected-text Ask Codex overlay, and a Help menu feedback entry. ### Performance improvements and bug fixes - Improved review diff whitespace handling and search highlighting. - Fixed in-app browser address bar and external-open issues, plus several file viewer and side-panel bugs. - Additional performance improvements and bug fixes.