design.md follow-ups matching the math.cs/HLSL fix in the previous commit:
- The F6 "5x5x5 is exact" argument is rewritten with the corrected near-side
neighbour bound (choose the axis closest to its own boundary, not a fixed
axis), the m <= 1/2 derivation, and the counterexample that showed the old
argument wrong. Same text as the math.cs comment, so the two do not drift.
- "Integer hashing" now states that cellular hashes the winning cell's
integer coordinate, not its float32 bit pattern, and records the measured
chi-square evidence (203.8 over 1,000,000 cells, 15 df, critical value
37.7) for why the old bit-pattern hash failed a uniformity check.
- "Precision domain" gets a new paragraph: the lower-bound prune's bit
identity to the unpruned 5x5x5 search holds for |p| < 2^25, not
unconditionally. Above that, cell + offset itself starts to round in
float32, so the pruned and unpruned loops can visit different actual
neighbours at the same nominal offset (Soul, cut 2a-i: 180 of 1,100,000
points differ at |p| ~= 3.4e7). This is a float32 domain limit on the
equivalence proof, not a bug in the prune; the committed test's [-50, 50]^3
sweep is comfortably inside it.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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