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/lang/alias_cgen_b6_test.ww

@@ -1,4 +1,4 @@
-// alias_cgen_b6_test — #5 alias arc F2b (B6 train): the cgen.c cgexpr/cgstmt
+// #5 alias arc F2b (B6 train): the cgen.c cgexpr/cgstmt
 // INLINE single-peel sweep through type_chase_named, by consumer family —
 // c1 assign/reassign, c2 call-arg, c3 addr-of/field-walk/index spine,
 // c4 cast/is/try, c5 reads/len/globals. Every K_RUN row was a cs-side
@@ -15,8 +15,6 @@
 
 package alias_cgen_b6_test;
 
-// ---- c1: assign/reassign family
-
 type c1sr_ms0 = str;
 type c1sr_ms = c1sr_ms0;
 
@@ -47,8 +45,6 @@ type c1da_st = c1da_st0;
 	assert(x.b == 9);
 };
 
-// ---- c2: call-arg family
-
 type c2fi_fs0 = struct { x: f64 };
 type c2fi_fs = c2fi_fs0;
 
@@ -84,8 +80,6 @@ fn c2st_g(s: c2st_ms) i64 = { return len(s): i64; };
 	assert(c2st_g(a) == 5);
 };
 
-// ---- c3: addr-of/field-walk/index spine
-
 type c3if_el0 = struct { a: i64, b: i64 };
 type c3if_el = c3if_el0;
 
@@ -190,8 +184,6 @@ type c3kc_S2 = struct { arr: [4]c3kc_my16, n: int };
 	assert(s.n == 9);
 };
 
-// ---- c4: cast/is/try family
-
 type c4sc_ms0 = str;
 type c4sc_ms = c4sc_ms0;
 
@@ -223,8 +215,6 @@ type c4is_u = c4is_u0;
 	assert(!(v is void));
 };
 
-// ---- c5: reads/len/globals family
-
 type c5tf_u0 = (void | i64);
 type c5tf_u = c5tf_u0;
 type c5tf_st0 = struct { f: c5tf_u, n: i64 };