fix: scope editor service in window title to own editor groups container (#306226)

* fix: scope editor service in window title to own editor groups container

The main window's WindowTitle used the global IEditorService which
tracks editor groups across all windows including auxiliary windows.
When a terminal was moved to a new window, the auxiliary window's
active editor change propagated to the main window's title, causing
it to incorrectly display the terminal name instead of the open file.

Scope the editor service used by WindowTitle to the window's own
editor groups container so each window title only reflects editors
within that window.

Closes #267538

* scope entire instantiator

* compile

* polish

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Co-authored-by: Benjamin Pasero <[email protected]>