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/200_parse.c

@@ -1,11 +1,7 @@
 /*
- * 200_parse — parser tests.
- *
- * Two flavours:
- *   1) "must parse": source must produce a Node and no errors.
- *   2) "shape match": parsed AST printed via astprint, compared against
- *      expected substring (so tests stay readable without binding to
- *      every position field).
+ * Shape rows compare astprint output against a substring, not a full
+ * golden, so tests stay readable without binding to every position
+ * field.
  */
 #include "ww.h"
 #include <stdio.h>
@@ -136,34 +132,20 @@ main(void)
 		"fn fnt(f: fn(i32) i32, x: i32) i32 = { return f(x); };",
 		"fn anontype() void = { let f: fn(i32) i32 = id; };",
 
-		/* multiple decls */
 		"import io;\nimport fmt;\ndef N: i32 = 8;\ntype p = struct{x:i32};\nfn f() void = {};",
-		/* attribute on FFI decl */
 		"@symbol(\"strlen\") fn cstrlen(s: *u8) u64;",
-		/* trailing comma */
 		"fn f(a: i32, b: i32,) void = {};",
-		/* nil/true/false */
 		"fn f() void = { let p: *i32 = nil; let x: bool = true; let y: bool = false; };",
-		/* chan */
 		"fn ch() void = { let c: chan i32; let v = <-c; };",
-		/* nested struct lit */
 		"fn lit2() void = { let q = box { p = nil, n = 0, items = [1, 2] }; };",
-		/* defer with call */
 		"fn f() void = { defer close(fd); return; };",
-		/* break / continue */
 		"fn f() void = { for () { if (x) { break; }; continue; }; };",
-		/* deeply nested expr */
 		"fn deep() i32 = { return ((((((1 + 2) * 3) - 4) / 5) % 6) << 7); };",
-		/* index chain */
 		"fn ix() i32 = { return a[b][c[d]]; };",
-		/* dot chain */
 		"fn dot() i32 = { return a.b.c.d; };",
-		/* call chain */
 		"fn cc() i32 = { return f()()(); };",
-		/* mixed postfix */
 		"fn mx() i32 = { return obj.method(arg)[idx].field; };",
 
-		/* multi-return tuples */
 		"fn divmod(a: i64, b: i64) (i64, i64) = { return a / b, a % b; };",
 		"fn try() (i32, str) = { return 0, \"\"; };",
 		"fn use_tuple() void = { let q, r = divmod(10, 3); };",