feat(cloud): warn on deprecated iOS 16 (removal 2026-08-23)

[finalerock44]

What

Adds a soft deprecation warning to dcd cloud when a test explicitly targets iOS 16 (--ios-version 16). iOS 16 is supported on only one device (iPhone 14) and is being sunset.

Part of the iOS 16 deprecation. This is Phase 1 (soft) — iOS 16 still runs during the grace period; the warning just nudges users to migrate. Enforcement (removing iOS 16 from the API compatibility lookup + the Mac-fleet runtime) lands separately on the removal date.

Behaviour

• Fires only on an explicit --ios-version 16. When the flag is omitted the API defaults to iOS 17, so there's no false warning.
• Non-fatal (warnOut → suppressed under --json), rendered via the standard ui.warn + ui.branch layer:

⚠ iOS 16 is deprecated
  ⎿ iOS 16 will be removed on 23 August 2026; after that, tests targeting it will fail.
    Switch to iOS 17 or newer — iPhone 14 also supports 17 and 18.
    See: https://docs.devicecloud.dev/getting-started/devices-configuration

Notes

• Removal date is 23 August 2026 (60-day grace window).
• The docs carry the matching notice.

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.