Initialize the root locale for NSHostingView on macOS

[Kyle-Ye]

Summary

NSHostingView creates an EnvironmentValues instance and passes it to the view graph without applying root environment configuration.

The default locale is Locale(identifier: ""), so Text(_:format:) passes an empty locale to Foundation instead of using the current system locale. This causes TextHeightUITests/dateFormatStyleExample() to fail on macOS.

Current behavior

For the fixed date used by TextFormatStyleExample, OpenSwiftUI renders:

• 2026-01-01
• 2026 M01 1, Thu 8:00:00 AM GMT+8
• 08:00

SwiftUI renders:

• 1/1/2026
• Thursday, January 1, 2026 at 08:00:00 GMT+8
• 08:00

Formatting an equivalent Date.FormatStyle directly with Locale(identifier: "") reproduces the OpenSwiftUI output.

Expected behavior

The macOS root environment should use the current system locale unless a view explicitly overrides it. TextHeightUITests/dateFormatStyleExample() should match the SwiftUI reference.

Implementation notes

• EnvironmentValues.configureForRoot() initializes locale, calendar, and timeZone.
• UIKit applies this configuration when constructing its root environment.
• NSHostingView.updateEnvironment() currently forwards a plain EnvironmentValues() without applying it.