Capability-matrix correctness fix: real 16i ladders use F (CNC->PMC) and
G (PMC->CNC) signal groups for handshakes, but PmcLetters(Sixteen_i) was
returning {X,Y,R,D} only. Widen to {X,Y,F,G,R,D}; M/C/E/A/K/T remain
0i-F / 30i-only. Updated the matching test row.
Closes #265