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single-PT_LOAD and no-archive claims, superseded ABI tables); every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/check.c

@@ -1,6 +1,4 @@
 /*
- * check.c — name resolution + type checking pass.
- *
  * Two-stage:
  *   1) collect: walk top-level decls and install Syms with stub types.
  *   2) resolve: expand types, check fn bodies and def initialisers.
@@ -1046,8 +1044,6 @@ resolve_type(Checker *c, Node *n)
 	}
 }
 
-/* ---- expressions -------------------------------------------------- */
-
 static Type *
 unify_arith(Checker *c, Pos p, Type *a, Type *b)
 {
@@ -2007,7 +2003,6 @@ cexpr(Checker *c, Node *n)
 			(void)cexpr(c, n->rhs);
 			return n->type = ty_void;
 		}
-		/* Reject assignment to a const-bound name. */
 		if (n->lhs && n->lhs->kind == N_IDENT && n->lhs->str) {
 			Sym *s = scope_lookup_prefer(c->cur, c->cur_mod,
 			    n->lhs->str);
@@ -2387,8 +2382,6 @@ cexpr(Checker *c, Node *n)
 	}
 }
 
-/* ---- statements --------------------------------------------------- */
-
 static void
 clet(Checker *c, Node *n)
 {
@@ -2731,8 +2724,6 @@ cstmt(Checker *c, Node *n)
 	}
 }
 
-/* ---- top-level ---------------------------------------------------- */
-
 static Type *
 build_fn_type(Checker *c, Node *fn)
 {