Harden COM port enumeration to avoid Bluetooth-driven startup/dropdown crashes

[Copilot]

On some Windows 10 systems, opening or initializing the COM port selector could crash Mission Planner when Bluetooth serial drivers stall or misbehave during port enumeration. This change makes COM discovery resilient so the UI remains responsive and usable even when a driver hangs or throws.

• Serial enumeration timeout + fallback

  • MissionPlanner.Comms.SerialPort.GetPortNames() no longer depends solely on System.IO.Ports.SerialPort.GetPortNames().
  • Added timeout-protected system enumeration path.
  • On timeout/failure (Windows), falls back to registry-backed COM discovery via HARDWARE\DEVICEMAP\SERIALCOMM.

• UI crash containment in port dropdown population

  • Wrapped PopulateSerialportList() COM port insertion path in guarded error handling.
  • Dropdown still populates baseline connection options even if COM discovery faults.

• Diagnostics improvements

  • Replaced generic exception logging with contextual messages for:
    • system port enumeration failures/timeouts
    • Windows registry COM fallback failures
    • serial dropdown population failures

private static string[] GetSystemPortNames()
{
    var ports = GetSystemPortNamesWithTimeout(SystemPortEnumerationTimeoutMs);
    if (ports != null) return ports;

    if (Environment.OSVersion.Platform == PlatformID.Win32NT)
        return GetWindowsRegistryPortNames();

    return Array.Empty<string>();
}

[Copilot]

Pull request overview

This PR aims to prevent Mission Planner startup/UI crashes and hangs caused by problematic serial/Bluetooth drivers during COM port enumeration by adding a timeout-protected enumeration path with a Windows registry fallback, plus additional guarding when populating the serial-port dropdown.

Changes:

• Added a timeout-based COM port enumeration path with Windows registry fallback (HARDWARE\DEVICEMAP\SERIALCOMM) in MissionPlanner.Comms.SerialPort.GetPortNames().
• Wrapped serial-port dropdown population in MainV2.PopulateSerialportList() with exception handling to keep the UI responsive.
• Updated logging to include more contextual error messages (but some new messages currently don’t match the code paths they’re in).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
MainV2.cs	Adds guarded COM port dropdown population and updates error logging around connection/setup paths.
ExtLibs/Comms/CommsSerialPort.cs	Introduces timeout-based system COM enumeration with Windows registry fallback for resilience.

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