CLAUDE: robust average v2: NO NaN frame - all contributors + median/IQR rejection

Andrey's correction: the eroded average left a wide NaN frame (and all
its descendants - EVAL diffs). The average virtual image must be defined
wherever ANY scene provides (a single bad first/last row/col at most):
combine ALL available contributors, let the count taper naturally near
the edges, and reject junk providers per pixel as OUTLIERS vs the MEDIAN
with an IQR-based robust sigma (immune to heavy contamination, unlike
mean/sigma). Fewer than 4 providers - plain mean; zero - NaN. Geometric
erosion (erodeDefined/erodedMasks/AVG_EDGE_ERODE) removed.

Next (Andrey): per-TILE outlier rejection in the 16-sensor TD
consolidation, anticipating the GPU migration (candidate indicator:
CC(0,0) flux, possibly + quadrant energy).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>