Per Andrey's continuity requirement: a sub-pixel target shift switching
between 1 and 2 surviving cells must not change the total injected energy
(filterConv5dROI does not conserve energy - it zeroes weaker components).

condition() now labels 4D-connected survivor clusters (3^4-1 connectivity,
BFS) and applies three regimes:
1. Single survivor: full 3x3x3x3 spread with fading peripherals (as before).
2. Compact cluster (2..curt_recur_max_clust near-equal survivors): spread
   limited along resolved dimensions; cluster total output = cluster max M,
   shared proportionally (survivor i contributes M*m_i/sum(m_j)) - exactly
   continuous across the 1<->2 survivor transition.
3. Cluster larger than curt_recur_max_clust (default 5): weak signal that
   passed the filter linearly - identity, no spreading/renormalization.

New parameter curt_recur_max_clust plumbed through dialog/properties/copy;
-RC<n> added to the -RECUR image titles.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>