client: fix two onboarding bugs:

1. indicate a fallback position for the tippy popup, since <main> is not
   present in onboarding.
2. allow scrolling the logs by settings the onboarding container's
   height to 100%.
1 job for finish-ts in 4 minutes and 3 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed ci #1286163

00:04:03