Deep-review follow-up on R13 S3.
- Add a roving-keyboard-nav test proving a disabled ActionMenu item is
skipped by arrow keys, and assert the stats "left" row renders the
formatEta value (formatEta had no coverage anywhere).
- Remove the disabledIndices plumbing from AnchoredPopover + ActionMenu:
it was redundant. useListNavigation already skips items via their DOM
disabled/aria-disabled attribute, and PopoverItem renders a native
disabled button — verified against @floating-ui/react 0.27
isListIndexDisabled and by a mutation test. Behaviour is unchanged and
now guarded by the new test.