test: banner purge + WHY-only comment sweep (rule 8)

Every section banner dies (103 -> 0) across test/lang, the observer
suites, the C carriers, and the five comment-heavy corpus fixtures;
banner provenance (#N cites, carrier numbers, repair-cluster labels)
folded into headers or adjacent WHY comments. Narration deleted; row
provenance, ref cites, divergence pins, and layout contracts kept
(fwd-ref decl-order guards and bootstrap-gate corpus rationale
restored where the sweep over-cut). Comment-only proven: all 3742
wwbuild workdir .s byte-identical before/after; test-commit and
test-byteid (161 lang + 1399 data, 0 pinned-divergent) green.

test/wcc/994_w6c_ww.c

@@ -1,11 +1,7 @@
 /*
- * 994_w6c_ww — explicit bootstrap gate for the ww-side w6c port.
- *
- * w6c_ww is a thin packaging of selfhost/cmd/wcc/cgen.ww: it slurps a
- * .ww file, runs lex+parse+cgen, and writes Plan 9 amd64 asm to the
- * file given by -o. The same cgen is reached through `wwdump_ww -c`,
- * so w6c_ww must produce byte-identical output to wwdump_ww -c on
- * every program — this test pins that.
+ * w6c_ww and `wwdump_ww -c` reach the same selfhost cgen, so they must
+ * produce byte-identical output on every program — this test pins
+ * that.
  *
  * (We do not diff against C-side `w6c` here: this carrier's oracle is
  * the wwdump_ww -c TOOL OUTPUT, not the tool binary. The C-vs-ww diff
@@ -354,7 +350,7 @@ main(void)
 		n++;
 	}
 
-	/* ---- Tier-C capstone (#46 c6, rob-c6-spec §2 / amendment-B; M4 #89) ---
+	/* Tier-C capstone (#46 c6, rob-c6-spec §2 / amendment-B; M4 #89).
 	 * The load-bearing M4 oracle: build w6c by SEPARATE compilation under
 	 * BOTH driver stages and prove they sep-produce byte-identical per-package
 	 * .s/.o/.wwi (cs==ww on the real tool's sep artifacts, rule 10). The