Learned-key stages, per-scheme plot styles, KM naming

exp_learned.py mirrors every structured result stage for the learned key
family at the same SNRs, frame counts and seeds, so Figs. 2, 3, 4 and 7
and Tables IV and VI can carry both realizations of keyed masking.

replot_security.py gains a style registry: colour identifies the scheme
and line style the role, so a curve learned in one figure reads the same
in the next. Previously OMA was grey in two figures and teal in a third,
and blue meant the eavesdropper in one figure and the permutation key in
another.

data/sec_jam_learned.csv

@@ -0,0 +1,8 @@
+jsr_db,blind,matched,nojam
+-10,0.117582,0.40832,0.062852
+-5,0.215158,0.657572,0.062852
+0,0.404244,0.851282,0.062852
+5,0.648786,0.94662,0.062852
+10,0.839218,0.982652,0.062852
+15,0.939304,0.994184,0.062852
+20,0.979206,0.99818,0.062852