Fix Settings tint color panel tracking

[yvette-carlisle]

Summary

• stop syncing the shared NSColorPanel color from SwiftUI updates while the tint panel is visible
• keep the panel initialized from the current tint only when opening it, so AppKit can own drag tracking

Validation

• cargo make fmt-swift
• cargo make lint-swift
• cargo make test-macos-native-host
• cargo make test-macos-native-host-stage
• ./scripts/build_and_run.sh run
• manual Settings > Appearance > Tint color retest passed