Fix double registration of default multitouch device

[Copilot]

MTDeviceCreateDefault() returns a device that may already exist in the list from MTDeviceCreateList(), causing duplicate callback registration and inflated device counts.

Changes

• Track registered devices in a Set<UnsafeMutableRawPointer> during startup
• Skip default device registration if already present in the set
• Add debug logging when duplicate is detected

var registeredDevices: Set<UnsafeMutableRawPointer> = []

// Register devices from list
for device in deviceList {
    registeredDevices.insert(device)
    // ... register callback
}

// Only register default if not already tracked
if let defaultDevice = getDefaultDevice(),
   !registeredDevices.contains(defaultDevice) {
    // ... register callback
}

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[Copilot]

Pull request overview

This PR fixes a bug where MTDeviceCreateDefault() could return a device pointer already present in the list from MTDeviceCreateList(), causing duplicate callback registration and inflated device counts.

Key Changes:

• Introduced a Set<UnsafeMutableRawPointer> to track registered device pointers during startup
• Added duplicate detection before registering the default device
• Added debug logging when a duplicate is detected