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/stof.ww

@@ -1,6 +1,6 @@
-// strconv — string-to-float. Mirrors ref/hare/strconv/stof.ha
-// (Hare in turn adapts Go): Eisel-Lemire fast path [1] with the
-// Simple-Decimal-Conversion slow path [2] (decimal.ww) as fallback.
+// Mirrors ref/hare/strconv/stof.ha (Hare in turn adapts Go):
+// Eisel-Lemire fast path [1] with the Simple-Decimal-Conversion slow
+// path [2] (decimal.ww) as fallback.
 //   [1]: https://nigeltao.github.io/blog/2020/eisel-lemire.html
 //   [2]: https://nigeltao.github.io/blog/2020/parse-number-f64-simple.html
 //