New document is marked unsaved before any edit

Creating a new document immediately marks it dirty: the tab shows the unsaved dot and closing it triggers the save/discard prompt even though nothing was edited.

Expected: a fresh document stays clean until the first user mutation. Likely something during document setup (initial page creation, layout recompute, colour-profile default) runs through the undo/dirty tracking instead of being applied as the baseline state.

Repro: File › New, then close the tab.