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/sep/sepimport_test.ww

@@ -84,8 +84,6 @@ fn cmpsepwork(label: str, csdir: str, wwdir: str) void = {
 	if (seen == 0) { fail(label, "no .s/.wwi in cs sepwork"); };
 };
 
-// ---- coloimport (#98) --------------------------------------------------
-
 @test fn coloimport() void = {
 	let td: str = testenv.fresh();
 	let inc: str = strings.concat(testenv.repo(), "/test/wcc/data/colo98");
@@ -116,8 +114,6 @@ fn cmpsepwork(label: str, csdir: str, wwdir: str) void = {
 	testenv.clean(td);
 };
 
-// ---- depmain (#99) -----------------------------------------------------
-
 // column-0 anchored `TEXT main,` labels across every .s under `dir`;
 // the leading '\n' prepend also counts a file-leading label.
 fn countbaremain(dir: str) i32 = {
@@ -183,8 +179,6 @@ fn depmainrow(label: str, entry: str, want: i32, deps: str,
 		"cc.s", "TEXT cc.main,");
 };
 
-// ---- declns modfn coexist (#23/#30) ------------------------------------
-
 @test fn declns() void = {
 	let td: str = testenv.fresh();
 	let lays: []str = ["modfn_coexist", "modfn_coexist_vbu"];
@@ -278,8 +272,6 @@ fn depmainrow(label: str, entry: str, want: i32, deps: str,
 	testenv.clean(td);
 };
 
-// ---- slttypepref (#58/#50 c1) ------------------------------------------
-
 // fresh two-directory tree per (row,driver); relative build with the
 // tree as cwd (canonical dir-package build, binary lands in cwd).
 fn sltbuild(drv: str, param: str) i32 = {