Agent working in background opens new terminal tab and steals focus

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### Windows Terminal version

1.24.11911.0

### Windows build number

10.0.26200.0

### Other Software

GitHub Copilot CLI v1.0.85

### Steps to reproduce

Let agent do some work that results in it running a command that at some point opens a new terminal tab while you're doing something else in a different program.

### Expected Behavior

If whatever AI agent is doing in the background involves opening a new Terminal tab, the Terminal should stay in the background and not disrupt my work.

### Actual Behavior

Whenever a new Terminal tab is open by agent working in the background, the whole Terminal window is brought up to the foreground and steals focus from whatever I was doing at the time.

Note: I think agents should not normally open new terminal tabs for running commands, and they usually don't, but sometimes it just happens, possibly as a result of ignoring instructions and executing something with `cmd /c` but it's beside of the scope of this issue. If they do any stupid things, they should be let to deal with it :)

Start by reproducing the behavior on Windows Terminal 1.24.11911.0 with GitHub Copilot CLI v1.0.85 while another application has focus. Trace the tab-opening path and focus changes; done means a tab opened by background agent work leaves Terminal in the background and does not steal focus.

Written by the indexing model from the issue text.