fix(editor): set window title from item title for datastore-item editors
Previously the editor only called updateWindowTitle() when opened
with a file path; datastore-item editors fell through to the static
"Editor" fallback. Result: every note-editing window showed up in
the Windows switcher and other consumers as "editor" — visually
indistinguishable.
The window-presenter (the standard interface for window appearance)
reads win.getTitle(), which is what document.title propagates to.
Each window self-presents its title; consumers don't case-by-case.
This fix completes the editor's side of that contract:
- Track currentItemTitle alongside currentItemId on item load.
- updateWindowTitle resolves filename → currentItemTitle → "Editor".
- Re-fire updateWindowTitle when the autosave path detects a title
change (first heading edit, etc.) and when a deferred-new-note
item is first created.