v2 design: independent masks + affinity-aware Wiener demultiplexer

Redesign after the independent-mask dominance finding: the affinity
now parameterizes the receiver (closed-form Wiener) instead of the
mask ensemble. New Theorem 1 (spectral closed form), floors
sqrt(1-b^2)/2 vs 1/2, full-cooperation bound with equality at b=1.
GPU (torch) Monte Carlo backend, decision-directed SIC baseline,
TikZ block diagram source, verification suite V1-V11.

data/mask_family_rev.csv

@@ -1,10 +1,10 @@
-snr_db,haar,wh
-0,0.05647200954133838,0.05310404690708958
-5,0.08330434028403662,0.07868202035026188
-10,0.1362057604122267,0.1321506210735374
-15,0.22743813806699198,0.22553342842896307
-20,0.3620849406777639,0.36807222557624214
-25,0.5112067973087223,0.5367516728593701
-30,0.6187704792155053,0.6693336605430739
-35,0.670208963249346,0.7373274649462636
-40,0.689340654075078,0.7636921461142663
+snr_db,haar,wh,wh_exact_mse
+0,0.056410143594257535,0.055201172281522305,0.9978637042641639
+5,0.085697923428379,0.08462585555389524,0.9933106958866119
+10,0.14458728155121206,0.14321016235277056,0.9794808036088943
+15,0.24451895691454412,0.2423005321621895,0.9407034531235695
+20,0.3882001306116581,0.3829878903925419,0.8522246733307839
+25,0.540928793400526,0.5299757443368435,0.7177656385302543
+30,0.6472152987122536,0.631390101313591,0.5997132909297943
+35,0.6973008319735527,0.6793428674340248,0.5366590532660485
+40,0.7159504926204682,0.6972508707642555,0.5119321745634079