Stop blindly probing a fixed list (which always included CAA): read the
auto-filled zone and only probe the RR types each owner actually has,
keeping SOA/NS at the apex. The recordTypes option still works as an
explicit override; missing zone falls back to the legacy default.
An unreachable resolver tells us nothing about propagation: it's neither
a disagreement nor an error in the zone. Surface it as a distinct
Unreachable state so it stops polluting warning counts and the
Disagreeing/Errored buckets.
