Previously, when opening a new project (one that was never opened
before), the window bounds restoration logic would fall through to
GPUI's default window sizing instead of using the last known window
bounds.

This change consolidates the window bounds restoration logic so that
both empty workspaces and new projects use the stored default window
bounds, making the behavior consistent: any new window will use the last
resized window's size and position.

Closes #45092 

Release Notes:

- Fixed new files and projects opening with default window size instead
of the last used window size.