Flaky test: omo-prompt.contract.test.ts 'offers omo commands with the reported label null' sees no commands #2085

Seen on #2081, which changes only scripts/chat-virtual-browser-qa.ts, in Integration tests (run 40565565799, job 122405886467, self-hosted runner):

error: expect(received).toContain(expected)
Expected to contain: "favorite-models"
Received: []
  at server/omo-prompt.contract.test.ts:183:22
(fail) slash commands follow the pane's process > offers omo commands with the reported label null [25.90ms]

The pane's command list was still empty when the test read it. The same run logged unrelated EIO: i/o error, fsync and fixture tab creation failed lines from other tests, so the runner was under load.

Expected: the test waits for the pane's omo commands to be reported before it asserts on them, instead of reading the list once.