Extend KOReader's cached menu order instead of persisting complete
override lists. Remove marker-owned legacy overrides during upgrade
while preserving hand-maintained entries.
Closes#1878
Squash of feat/koreader-widget-board. KOReader plugin 2.0.0 gets the widget-board dashboard, redesigned
book details, menus, lists and dialogs, Decor page and reading companions. Highlights, notes and bookmarks
now stay in step across web, Kobo, KOReader and the phones (defects D-00 to D-20, migration 0121), and
reading progress and narration hand off cleanly between devices.
neon