Show HN: Penmentor – Claude marks up your handwritten math like a teacher

Penmentor is a tool that allows users to get handwritten math marked up by AI models like Claude, Gemini, or GPT. By pressing a key while working, users can have their work reviewed. It supports various agents such as claude:opus, claude:sonnet, claude:haiku, and codex:gpt-5.6-terra, as well as Antigravity CLI agents like agy:gemini-4-argon-medium. Penmentor is released under the MIT license.