Add monitor connection events

[PrzemyslawKlys]

Summary

• extend MonitorWatcher with MonitorConnected and MonitorDisconnected
• use WM_DEVICECHANGE notifications via new DeviceChangeWindow
• expose native device change constants
• test monitor connection and disconnection handling

Testing

• dotnet test Sources/DesktopManager.Tests/DesktopManager.Tests.csproj --framework net8.0

---

https://chatgpt.com/codex/tasks/task_e_686d81246e8c832e9eab4c94717cded0

[codecov]

Codecov Report

Attention: Patch coverage is 83.82353% with 11 lines in your changes missing coverage. Please review.

Project coverage is 52.32%. Comparing base (417a80c) to head (f001802).
Report is 15 commits behind head on v2-speedygonzales.

Files with missing lines	Patch %	Lines
Sources/DesktopManager/MonitorWatcher.cs	83.58%	5 Missing and 6 partials ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##           v2-speedygonzales     #106      +/-   ##
=====================================================
+ Coverage              50.69%   52.32%   +1.63%     
=====================================================
  Files                     26       28       +2     
  Lines                   1298     1397      +99     
  Branches                 200      217      +17     
=====================================================
+ Hits                     658      731      +73     
- Misses                   571      588      +17     
- Partials                  69       78       +9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.