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/ascii/ascii_test.ww

@@ -1,6 +1,5 @@
-// asciitest — exercises lib/ascii case folding. Run with
-// `ww run lib/ascii/asciitest.ww`. A failing row aborts via the
-// assert/abort builtin (task #5 @test conversion).
+// A failing row aborts via the assert/abort builtin (task #5 @test
+// conversion).
 //
 // Vectors mirror Hare's @test fn strcasecmp in ref/hare/ascii/string.ha.