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/crypto/sha256/sha256_test.ww

@@ -1,13 +1,11 @@
-// sha256_test — exercises lib/crypto/sha256 against the standard NIST
-// SHA-256 vectors (FIPS 180-4 examples + the classic "one million a's").
-// Run with `out/bin/ww run lib/crypto/sha256/sha256_test.ww`.
+// Vectors: the standard NIST SHA-256 set (FIPS 180-4 examples + the
+// classic "one million a's").
 //
 // The digest is the cgen-correctness oracle for u32 wrapping arithmetic
 // + the hash-vtable dispatch: any u32-overflow / rotate miscompile shows
 // up as a byte mismatch. A failing row aborts via the assert/abort
 // builtin (task #5 @test conversion). Expected digests come through the
-// (separately tested)
-// hex.decodestr so the vectors stay readable.
+// (separately tested) hex.decodestr so the vectors stay readable.
 package sha256_test;
 
 import bytes;