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_def_addr_test.ww

@@ -1,4 +1,4 @@
-// alias_def_addr_test — address-of a def whose declared type is an ALIAS of
+// Address-of a def whose declared type is an ALIAS of
 // an array/struct (#5 alias arc F2a, task #88), migrated from
 // test/wcc/944_alias_def_addr_run.c. defisaddressable (cgen.ww) keyed the
 // array leg on the UNCHASED syntactic dtnode (N_TARRAY), so `&D` where D is a
@@ -20,7 +20,6 @@
 
 package alias_def_addr_test;
 
-// def_ctrl — plain [3]int def, no alias; the always-held control.
 def Dctrl: [3]int = [1000: int, 2000: int, 3000: int];
 
 @test fn alias_def_addr_ctrl() void = {