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/strconv/ftos_data.ww

@@ -1,4 +1,3 @@
-// strconv — Ryū float→string lookup tables + bit-count constants.
 // Mirrors ref/hare/strconv/ftos_ryu.ha:159-222 byte-exact. Pure data
 // fold (strconv #106 fold-5): no logic, consumed by ftos.ww's
 // f64computeinvpow5 / f64computepow5 (the Ryū power-of-five cores).