toolchain: banner purge + WHY-only comment sweep (rule 8)

selfhost/, cmd/, internal/ join the tree-wide sweep: every section
banner dies (91 selfhost + the cmd C-style dividers -> 0); narration
and stale contracts deleted (pre-#22 bundler notes, retired
single-PT_LOAD and no-archive claims, superseded ABI tables); every
ref/harec/qbe cite, task cite, encoding/ELF contract, and rule-10
twin pointer kept; lost lifetime/rationale lines restored where the
sweep over-cut (elf_globals ownership, kwtab linear-scan). Comment-
only proven: all five wwstage tool binaries byte-identical across
the sweep; test-commit, test-byteid (161+1399, 0 pinned-divergent),
and test-bootstrap (fixed point + 991-995 byte-id) all exit 0.
The read-through banked 66 latent-bug leads (checkpoint).

cmd/wcc/type.c

@@ -1,10 +1,6 @@
 /*
- * type.c — Type values and structural equality.
- *
  * Built-in types are constructed once and exposed as globals so the
- * rest of the compiler can `==`-compare them. Compound types (ptr,
- * slice, array, fn, struct, chan) are constructed on demand and
- * de-duplicated when equality is cheap (only ptr/slice for now).
+ * rest of the compiler can `==`-compare them.
  */
 #include "ww.h"
 #include <string.h>
@@ -147,8 +143,7 @@ type_named(Arena *a, const char *name, Type *under)
 	return t;
 }
 
-/* type_chase_named — walk the TY_NAMED.under chain to the deepest non-
- * named type. Chain-of-aliases (#22): `type b = a; type a = struct;`
+/* Chain-of-aliases (#22): `type b = a; type a = struct;`
  * stacks two TY_NAMED layers — a single peel leaves `t` pointing at
  * the inner alias (still TY_NAMED), so kind-gated arms (TY_STRUCT,
  * TY_SLICE, TY_TAGGED, TY_PTR) miss and the consumer silently falls
@@ -372,7 +367,6 @@ type_assignable(Type *dst, Type *src)
 		}
 	}
 
-	/* Untyped → typed: only if the typed kind can hold the value. */
 	if (type_isuntyped(src)) {
 		Type *du = type_chase_named(dst);
 		if (src->kind == TY_UNTYPED_INT && type_isnum(dst)) return 1;