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/bytes/index_test.ww

@@ -1,6 +1,4 @@
-// indextest — exercises bytes.index/rindex, u8 and []u8 arms. A
-// failing row aborts via the assert/abort builtin (task #5 @test
-// conversion). Vectors mirror ref/hare/bytes/index.ha.
+// Vectors mirror ref/hare/bytes/index.ha (task #5 @test conversion).
 
 package bytes_test;