Surface known limitations more prominently in compiler docs

[Keinberger]

The compiler index page already mentions that known bugs and limitations exist and links to the issue tracker, which is good. However, the detailed known-limitations doc (docs/external/src/appendix/known-limitations.md) that actually lists specific limitations is marked draft: true, so it doesn't render in the published docs. The appendix index linking to it is also marked draft: true.

This means the detailed information exists but isn't reachable. Pioneer developers are discovering these limitations during development rather than upfront.

I think we should remove the draft: true flags and make sure the index page links to the full known-limitations page directly, not just to the issue tracker.

[bitwalker]

We can certainly do that, though I will need to go through and review what's there, and where things stand today, because I believe things have drifted from ground reality a fair bit by now.

I'll try to get that done in the next few days, but it may have to wait until I'm back from vacation.