lib: banner purge + WHY-only comment sweep (rule 8)

Every // ---- section banner dies (132 -> 0): names carry the WHAT.
Narration deleted (filename restatements, run-with lines, what-the-
next-line-does); every ref/hare cite, task cite, divergence, ABI/
layout contract, and ownership qualifier kept (borrowed-view lines
restored where the sweep over-cut). Comment-only proven: all 442
walk-workdir .s and 32 import-probe .s byte-identical before/after;
libbyteid 56-roster all-ID.

lib/math/math.ww

@@ -1,6 +1,6 @@
-// math — numeric helpers. Subset of Hare's math::; only the absolute-
-// value pair for the signed integer types we currently care about. The
-// return type is unsigned so that abs(I32_MIN) doesn't overflow.
+// Subset of Hare's math::; only the absolute-value pair for the signed
+// integer types we currently care about. The return type is unsigned
+// so that abs(I32_MIN) doesn't overflow.
 
 package math;