"useAnyExisting" ignored with default terminal, allowHeadless, and globalSummon

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### Windows Terminal version

1.19.3172.0

### Windows build number

Version 22H2 (OS Build 19045.3758)

### Steps to reproduce

1. Make Windows Terminal the default terminal for the OS.
1. Add these to default config:
```json
"compatibility.allowHeadless": true,
"windowingBehavior": "useAnyExisting",
"actions":
[
{
"command":
{
"action": "globalSummon"
},
"keys": "ctrl+`"
},
```
2. Sign out of Windows and sign back in
3. Launch an instance of Windows Terminal
4. Use the global summon keys, Ctrl+`

### Expected Behavior

Global summon summons/hides the existing instance.

### Actual Behavior

A new terminal window appears for each press of global summon.

Start by tracing the globalSummon action with compatibility.allowHeadless and windowingBehavior set to useAnyExisting, focusing on how the default Windows Terminal instance is selected. Reproduce the Ctrl+` sequence after sign-in and verify that it summons or hides the existing instance instead of creating a new window on each press.

Written by the indexing model from the issue text.