Step 6 of the gui/app.py + gui/preview.py structural refactor — the
biggest single move in the sequence. The entire 1046-line popout
window class moves to its own module under popout/, alongside the
viewport NamedTuple it depends on. The popout overlay styling
documentation comment that lived above the class moves with it
since it's about the popout, not about ImagePreview.
Address-only adjustment: the lazy `from ..core.config import` lines
inside `_hyprctl_resize` and `_hyprctl_resize_and_move` become
`from ...core.config import` because the new module sits one package
level deeper. Same target module, different relative-import depth —
no behavior change.
preview.py grows another re-export shim so app.py's two lazy
`from .preview import FullscreenPreview` call sites (in
_open_fullscreen_preview and _on_fullscreen_closed) keep working
unchanged. Shim removed in commit 14, where the call sites move
to the canonical `from .popout.window import FullscreenPreview`.
