Make bot react to edits of manimate commands

It would be nice if the bot can detect when the code in a previous manimate command was changed, and have it delete the old rendering and rerender the animation.

Start by tracing how the bot handles a previous manimate command, stores or detects its code, deletes the old rendering, and starts a new render. Clarify the edit-detection trigger and expected behavior before implementation. Done means an edited command reliably removes its previous rendering and produces an updated animation.

Written by the indexing model from the issue text.