_healNonFinite(): on a divergence break, every non-finite node position
resets from its nearest finite neighbour (ring flood, corners re-seeded from
anchors if the whole cloth is gone), prev matched so verlet reads zero
velocity out of the heal, non-finite water zeroed (second wire behind the
break's dumpPond, unit-asserted so it can't rot). Deterministic, emits
'heal' {nodes, t}. Existing divergence-break test untouched and green.
Three new asserts (45/45 headless): finite-in-1s + prev matched + byte-equal
across two poisoned runs; NaN pond zeroed under live rain + direct-heal
water contract; negative control (honest overload breaks never heal).
Mutations, each red-then-green: heal off; prev left NaN; water zeroing off.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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