Move the hardcoded keytip sequence list into keytip_table.rs as the single
source of truth for both the matcher and the ribbon badge painter.
- Generalize Action::Home into Action::Tab(&'static str); the legacy
Edit/Format prefix special-case in lib.rs is absorbed into the table.
- Badge helpers: tab_sequence (tabs), group_extension (menu anchors),
item_letter (menu items), control_badges (command controls).
- Add tab letters for Insert (N), Page Layout (P), Formulas (M), Data (A),
Review (R), View (W); Draw/Automate stay unbadged until contextual
letters land.
- Tests: 5 table unit tests + tab_letters_switch_to_their_ribbon_tabs
integration test. All 7 xtask ci gates green.