Fix selection on MacOS clients

[o0101]

Issue is that the Meta key ⌘ is not correctly captured on client and transmitted as control key. It's platform-platform dependent.

This means that the control sequence that activates select depends on:

what key we capture on client,
what key we transmit to server
what key on server platform actually maps to select

We currently do not account for this, and it errors in the following way:

• we assume server platform is linux even when it's not, so we do not transmit correct meta key sequence if running on MacOS to trigger a select
• i'm not sure if we capture meta key correctly when we are on MacOS client (but we probably do as the web platform I think abstracts away from that by providing a Meta key which is somewhat cross-platform, encompassing ⌘ on Mac and the relevant one on other platforms).

Anyway this is one of those x-platform issues! Fun ! hahaha. And there's lots of them :)