Integrate rgbds-live

@daid 's RGBDS-live is a super cool tool that I'd love to see it integrated in Pan Docs for the ASM snippets we have here.

It's quite a big deal to implement such integration, but I actually see two big things a template-able minimal rgbds-ui should support:

- Hide code: snippets require some init code before/after, this code must be hidden if not explicitly requested but still executed/accessible
- Expose registries and peripherals. Each snippet explains something that can be understood by looking at what changed in the other registries or in the peripherlas (e.g. display). This must be configurable snippet-wise

In the end, code snippets will look very similar to what they are now, with just a couple of UI additions enabling users to run and play with the snippets, immediatly seeing the (scoped) effect on hardware.

Start by reviewing the existing Pan Docs ASM snippets and the proposed RGBDS-live integration. Determine how snippet initialization, hidden code, registries, and peripherals are currently represented; done means users can run snippets with configurable visibility and observe scoped hardware effects. No files or tests are named in the issue.

Written by the indexing model from the issue text.