mobai-ci v0.7.3

Steadier first step after an app launch

A step that opened the app could fail on its very next screen read with
"Error getting main window", because the app had not finished starting yet.
Screen reads now wait up to 10 seconds for a launching app instead of failing
the run.

Cloud simulators

The simulator runner is self-contained again, so it starts on cloud
simulators that have no local Xcode to lend it test frameworks. The runner in
0.7.1 and 0.7.2 crashed on start there.