Add per-display selection for ring light effect

[Copilot]

Ring light currently appears on all connected displays. Users with multi-monitor setups need to limit it to a specific display.

Changes

Model & Persistence

• Added selectedDisplayID: UInt32 to RingLightSettings (0 = all displays)
• Wired through controller to engine via update() signature

Display Filtering

• RingLightEngine.realizeWindowsIfNeeded() now filters screens:

  if selectedDisplayID != 0 && identifier.rawValue != selectedDisplayID {
      return nil
  }

UI

• Display picker in ContentView populates via availableDisplays()
• Shows "All Displays" + enumerated screens using NSScreen.localizedName
• Bound to @Shared(.ringLightSelectedDisplayID) for persistence

Default behavior unchanged (all displays). Selection persists across launches.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Specify display to show light on</issue_title>
<issue_description>Add the ability to limit the ring light to a specific display so it doesn't appear on every monitor that is connected to the laptop.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Specify display to show light on #7

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[Aayush9029]

@copilot verify that correct api is being used, use web / search tool if needed

[Copilot]

@copilot verify that correct api is being used, use web / search tool if needed

✅ API verification complete. The implementation uses the correct Apple APIs:

Screen Identification:

• NSDeviceDescriptionKey("NSScreenNumber") → Returns CGDirectDisplayID (UInt32)
• Standard approach per Apple docs, stable across reconnections

Display Names:

• NSScreen.localizedName → Available since macOS 10.15
• Returns user-friendly names (e.g., "Built-in Retina Display")
• Deployment target is macOS 14.0, fully compatible
• Fallback to "Display N" for empty names

Screen Collection:

• NSScreen.screens → Standard API for all connected displays

All APIs are modern, correct, and follow Apple's best practices. No changes needed.

References:

• https://developer.apple.com/documentation/appkit/nsscreen/3228043-localizedname
• https://developer.apple.com/documentation/appkit/nsscreen/1388369-devicedescription