test: re-cite retired-mechanism comments in surviving carriers

The migrate-and-retire audit left the surviving carriers as the only
files still describing the retired combined.ww amalgamator as live:
m2wwi/m3sep headers claimed .wwi was dead code, four byteid carriers
carried dead cleanup of never-written .combined.ww intermediates, and
sepbuild's enumeration mirror plus lib_byteid's completeness scan
still skipped the retired artifact form (the same silent
accommodation just removed from both drivers — dropping it here
surfaced and flushed 39 stale untracked amalgamator outputs across
lib/, which the gates now reject loudly). Remaining mentions are
past-tense history or quoted diagnostics.

test/wcc/994_w6c_ww.c

@@ -7,10 +7,9 @@
  * so w6c_ww must produce byte-identical output to wwdump_ww -c on
  * every program — this test pins that.
  *
- * (We do not diff against C-side `w6c` here because the C compiler has
- * features the ww cgen has not yet ported — float compare, fn-address
- * @symbol, indirect call. Test 990 probe 5 covers the C-vs-ww diff on
- * the subset that the ww cgen handles today.)
+ * (We do not diff against C-side `w6c` here: this carrier's oracle is
+ * the wwdump_ww -c TOOL OUTPUT, not the tool binary. The C-vs-ww diff
+ * on real programs is owned by the blanket byte-identity gates.)
  */
 #include <stdio.h>
 #include <stdlib.h>
@@ -189,9 +188,8 @@ main(void)
 	char cwd[1024];
 	if (getcwd(cwd, sizeof cwd) == NULL) return 1;
 
-	/* In-source corpus: programs the ww-side cgen handles today.
-	 * Mirrors probe 5 in 990_selfhost without the parts that drift
-	 * against C w6c. */
+	/* In-source corpus: programs the ww-side cgen handles today,
+	 * kept free of the parts that drift against C w6c. */
 	struct { const char *label; const char *src; } progs[] = {
 		{ "ret42",
 		  "fn main() i32 = { return 42; };" },
@@ -360,9 +358,9 @@ main(void)
 	 * The load-bearing M4 oracle: build w6c by SEPARATE compilation under
 	 * BOTH driver stages and prove they sep-produce byte-identical per-package
 	 * .s/.o/.wwi (cs==ww on the real tool's sep artifacts, rule 10). The
-	 * combined corpus + the sep-out==combined-out leg are gone — combined-mode
-	 * is being retired (E3 flip), so combined.ww is no longer fed as compiler
-	 * INPUT; the per-pkg cs==ww comparison is the surviving live oracle. Its
+	 * combined corpus + the sep-out==combined-out leg are gone with the
+	 * retired combined mode (E3 flip); the per-pkg cs==ww comparison is
+	 * the surviving live oracle. Its
 	 * cold pid-keyed scratch is wiped after the explicit bootstrap gate. */
 	{
 		char inc[4096], cmd[16384];