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/object/asmgate_test.ww

@@ -52,8 +52,6 @@ fn assemble(td: str, tool: str, tag: str, src: str, obj: str) i32 = {
 	return runcode(td, tag, av);
 };
 
-// ---- parsenum (530) ----------------------------------------------------
-
 @test fn parsenum() void = {
 	let td: str = testenv.fresh();
 	let labels: []str = ["ws_after_dollar", "leading_zero",
@@ -108,8 +106,6 @@ fn assemble(td: str, tool: str, tag: str, src: str, obj: str) i32 = {
 	testenv.clean(td);
 };
 
-// ---- datargate (989) ---------------------------------------------------
-
 @test fn datargate() void = {
 	let td: str = testenv.fresh();
 	let bads: str = strings.concat(td, "/bad.s");