ci: check for unused snippets

[gcomte]

Fails snippet CI when an anchored source snippet is unused.

Temporarily excludes React Native snippets until September 11, 2026 because the React Native library is not yet ready. The snippets will be reintroduced once the React Native library is on SDK version 0.10.0 as well.

[86667]

Im not convinced that this is necessary - what is the harm in having some unused snippets really?

Also, a linter would likely be an easier way to identify unused code.

This feels like polish which will only get in the way whilst the repo is in its current development stages

[gcomte]

what is the harm in having some unused snippets really?

The goal is to protect us from unnecessary maintenance work.
Granted, it introduces new maintenance work which is taking care of the checker.

Also, a linter would likely be an easier way to identify unused code.

I don't see how you would achieve the same thing with a linter

This feels like polish which will only get in the way whilst the repo is in its current development stages

How would it get in our way? You mean if you created a snippet, but don't want to reference it in the docs yet? Then you could just exclude it, right? At least you are conscious that there is 'dead code' or rather 'dead docs'.

[gcomte]

Blocked: Won't be merged until we're done with a major restructuring of the docs.