'v4' is deprecated: watchOS 9.0 is the oldest supported version

[skyfoxa]

Summary

Building with Xcode 27 emits a deprecation warning from the package manifest:

'v4' is deprecated: watchOS 9.0 is the oldest supported version

This is caused by .watchOS(.v4) in Package.swift. Xcode 27 dropped support for watchOS 4–8 SDKs, making watchOS 9.0 the minimum platform version recognized by SPM.

Fix

Update .watchOS(.v4) to .watchOS(.v9) in Package.swift.