tindy2013/subconverter ? reverse-engineered prompt

Build me a small tool that can take subscription links from different proxy apps and turn them into the format another app needs. I want to be able to paste in one link or merge a few links together, then get back a clean converted subscription for things like Clash, Quantumult, Quantumult X, Surge, V2Ray, Shadowrocket style outputs, and similar formats.

It should run locally with a simple web page or local URL that I can open in the browser, and I should be able to pass in a target format, the source subscription URL, and an optional config file if needed. Please make it easy to use with defaults so I do not have to set up a lot just to get started. If it makes sense, also include an option to upload the generated result to Gist automatically using a token. Keep it reliable, lightweight, and focused on conversion rather than fancy UI.