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/xmod/m1_test.ww

@@ -82,8 +82,6 @@ fn mkdirs(td: str, dirs: []str) void = {
 	};
 };
 
-// ---- m1mangle (#22 + #32) ----------------------------------------------
-
 // dirs are '/'-joined mkdir steps, parents before children.
 fn m1row(label: str, dirs: []str, rel: str, content: str, root: str,
 	want: i32) void = {
@@ -163,8 +161,6 @@ fn m1row(label: str, dirs: []str, rel: str, content: str, root: str,
 		"export fn main() int = { return cc.val(); };\n"), 3);
 };
 
-// ---- m1usehint (#40) ---------------------------------------------------
-
 fn uselayout(td: str, apick: str, onecall: str) void = {
 	let dirs: []str = ["a", "a/math", "b", "b/math", "one", "two"];
 	mkdirs(td, dirs);