Fix React 18 compatibility

[mbrinkl]

Fixes broken client in react 18 strict mode.

Closes #1068, #1073, #1096

The issue: WrappedBoard unmounts and remounts in strict mode, and the debug panel did not unsubscribe the clients when it was destroyed.

Checklist

• Use a separate branch in your local repo (not main).
• Test coverage is 100% (or you have a story for why it's ok).

[delucis]

Wow, amazing work tracking that down — thank you @mbrinkl!

I’ve tested this out locally, including wrapping the example app in <StrictMode> as that was reported as causing the problem in #1068 and everything appears to be working as expected. 🥳

[mbrinkl]

Whoops, I had strict mode when debugging but then I recreated in a new branch and forgot to include it, thanks for catching that.