A typo'd subcommand fell through the dispatcher to the plan-hook path,
which reads the hook payload from stdin. From a terminal that stdin never
closes, so `plannotator annotatte README.md` hung with no output instead
of reporting the typo.
Reject an unrecognized first token before the dispatcher runs: print the
offending word, the nearest documented command, and a pointer to --help,
then exit 1. Flags and the no-argument hook invocation are left alone so
the real hook path is untouched.
Martin Sumera