nvim-telescope/telescope.nvim ? reverse-engineered prompt

Build me a Neovim plugin in Lua that works like a fast fuzzy finder for files, buffers, help pages, search results, and other lists inside the editor.

I want a clean popup interface where I can type to filter results, move through matches, preview the selected item, and open it in the current window, a split, a vertical split, or a new tab. It should feel easy to use right away, but also be flexible so I can customize key mappings, layouts, sorting, and per picker settings.

Please include a few useful built in pickers like finding files, live grep, open buffers, and help tags, plus support for extensions so more pickers can be added later. Use Lua throughout, keep it modular, and make sure it integrates well with modern Neovim. If you need to check current Neovim or plugin docs online, go ahead.