New instance behavior doesn't work as expected with multiple monitors

### Windows Terminal version

1.15.2713.0

### Windows build number

10.0.22621.0

### Other Software

_No response_

### Steps to reproduce

* You need at least 2 monitors connected.
* Set "New instance behavior" to "Attach to most recently used window on this desktop".
* Open Terminal window and move it to other monitor.
* Open another Terminal

### Expected Behavior

Since first Terminal window is on different monitor, the second one should open new window.

### Actual Behavior

Second terminal is opened as a tab in the window moved to second monitor.

No source files, tests, or entry points are named. First reproduce this on Windows with two monitors and the specified “New instance behavior,” then trace the handling of new Terminal launches and monitor placement. Done means a second launch opens a new window when the existing window is on another monitor, while preserving the configured tab behavior otherwise.

Written by the indexing model from the issue text.