Fix CI flakiness: data-stream races, QoS inversions, deterministic tests #1690

Job	Run time
Check Changes	5s
Check Protocol	20s
Lint	20s
App Size	4m 29s
Build & Test (macos-26, 26.6, iOS Simulator,name=iPhone 17 Pro,OS=26.5, true)	17m 18s
Build & Test (macos-15, 16.4, iOS Simulator,name=iPhone 16 Pro,OS=18.5)	13m 53s
Build & Test (macos-26, 26.6, iOS Simulator,name=iPhone 17 Pro,OS=26.5, true)	14m 6s
Build & Test (macos-15, 16.4, macOS)	12m 51s
Build & Test (macos-26, 26.6, macOS, true)	15m 47s
Build & Test (macos-26, 26.6, macOS,variant=Mac Catalyst)	14m 6s
Build & Test (xcode-27, latest, macOS,variant=Mac Catalyst)	12m 59s
Build & Test (macos-26, 26.6, macOS, true)	13m 52s
Build & Test (macos-26, 26.6, macOS, true)	14m 54s
Build & Test (macos-26, 26.6, macOS, true)	13m 22s
Build & Test (xcode-27, latest, iOS Simulator,name=iPhone 17 Pro,OS=27.0)	23m 10s
Build & Test (macos-26, 26.6, visionOS Simulator,name=Apple Vision Pro,OS=26.5)	12m 39s
Build & Test (macos-15, 16.4, tvOS Simulator,name=Apple TV,OS=18.5)	11m 6s
Build & Test (macos-15, 16.4, macOS,variant=Mac Catalyst)	13m 3s
Build & Test (xcode-27, latest, macOS)	12m 44s
Build & Test (xcode-27, latest, tvOS Simulator,name=Apple TV 4K (3rd generation),OS=27.0)	10m 22s
Build & Test (macos-26, 26.6, tvOS Simulator,name=Apple TV,OS=26.5)	11m 0s
Build & Test (xcode-27, latest, visionOS Simulator,name=Apple Vision Pro,OS=27.0)	12m 44s
Build Docs	19s
	4h 15m 29s

Provide feedback