Parse Parrot's common.xml and ardrone3.xml into CommandSpec objects rather
than transcribing 264 commands by hand. Direction is derived from
comment result=/triggered= with a class-name-suffix fallback for the 31
commands that state neither, giving 101 to-drone and 163 from-drone.
ardrone3.Piloting.FlatTrim is injected: the firmware accepts it but neither
the vendored snapshot nor upstream defines it.
codec encodes the <BBH header (the command id is 16 bits, not 8) and reads
enums as i32 and strings as NUL-terminated, both of which pyparrot gets
wrong. safety assigns the arming tier by class, with Mavlink and Calibration
counted as motion because they move the aircraft. expectations parses the
undocumented #p-c-m grammar including | alternatives and this.<arg> echoes.
90 tests, counts asserted so a bad parse fails loudly.
