Final revision: audit fixes, cross-scheme comparisons, known-plaintext stage

- exclude the all-ones Walsh-Hadamard row and test every key family
  against the all-ones guess
- pass the model dimension to the noise scaling so the key-length sweep
  runs at a fixed per-dimension SNR
- known-plaintext attack with nested accumulation and common random
  numbers, averaged over 40 collections
- key sensitivity and brute-force search extended to the permutation
  key and the index cipher
- make_tables regenerates all three result tables from the CSVs

data/sec_sens_cmp.csv

@@ -0,0 +1,11 @@
+frac,ser_mask,ser_perm,ser_pad
+0,0.99998375,0.9999833333,0.9999847412
+0.2,0.9997954167,0.9996233333,0.999859778
+0.4,0.9985329167,0.9949383333,0.9987114181
+0.6,0.99153625,0.9540933333,0.9881584643
+0.75,0.9644704167,0.880335,0.9375
+0.85,0.88742875,0.7279433333,0.8105354292
+0.9,0.7780379167,0.5716733333,0.6701230223
+0.94,0.6256225,0.4316466667,0.4859430867
+0.97,0.43810125,0.3708666667,0.283022376
+1,0.2756983333,0.3021566667,0