Render error when model fails

[sverhoeven]

Fixes #119

TODO

• the error of the model is shown for a moment and is then removed. The error toast should persist forever.
• remove

  class-web/packages/class/src/runner.ts

  Lines 44 to 47 in 08b093c

  	// TODO remove when we see this error rendered
  	if (config.runtime === 42_000) {
  	throw new Error("Runtime cannot be 42_000 seconds.");
  	}