CDN-343: The Concentration Prior Stress Test - Art Edition

CDN-343 stress-tests the CDN-342 last-lens concentration debt against a locked lognormal concentration prior centered on the CDN-335 fiducial value c0=10.0 with sigma_log10(c)=0.15 dex. The J1100+5329 BE crossing occurs at c=13.174, only 0.798 sigma above the prior median, with a 21.2% upper-tail probability. The simple-boosted crossing occurs at c=12.791, and the full-sample 20/20 pass point at c=15 remains only 1.174 sigma above the fiducial prior. Verdict: LAST_LENS_CROSSING_WITHIN_ONE_SIGMA.