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/encoding/base32/base32.ww

@@ -1,5 +1,3 @@
-// encoding/base32 — RFC 4648 base32 encode/decode, buffer-based.
-//
 // Mirrors Hare's encoding::base32 surface, modulo Hare's stream-based
 // encoder/decoder. ww ships the in-memory subset only: `encode(dst,
 // src)` writes the encoded bytes into `dst`, returning the count;