Problem:
An insert-session entered by a scheduled `feedkeys('i','n')` is
classified on entry (as "not typed"), and not reevaluated after that,
thus user input following it is not captured.
Repro: an `:imap` that does `feedkeys('<esc>','n')` and schedules
re-entering insert, emits one CmdAtom for the first press, then nothing
else.
Solution:
Sample `maptick` (ticked by `gotchars()` on typed input, including
mappings) at session start; if it advanced by session end, the session
is user input.