wait stable times out with 0 captures on the iOS Simulator #2885

Problem

wait stable on the fixture Automation lab screen (iOS Simulator, iPhone 17 Pro / iOS 26.2, AX-bridge captures) timed out with 0 captures in 15 of 16 calls on 2026-09-24. A timeout could be expected on a screen that keeps changing, but zero captures means the command never observed the surface at all.

Required behavior

• wait stable takes captures and compares them until the surface stops changing or its deadline expires.
• A timeout reports what it saw: the capture count and why stability was not reached, as typed details.
• If something stops captures from being taken (routing, a pending post-gesture record, a bridge preparation gate), the reason is reported, not a silent zero.

Evidence

Found while fixing the longpress flake (#2883). The worker tried wait stable as the settle step after an unsettled scroll and dropped it because of this. Reproduce with repeated wait stable calls right after a scroll down 0.75 on the Automation lab list.