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single-PT_LOAD and no-archive claims, superseded ABI tables); every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

selfhost/cmd/wcc/cgendecl.ww

@@ -1,24 +1,9 @@
-// selfhost/cmd/wcc/cgendecl.ww — split out of cgen.ww.
-//
-// Houses the top-level emission glue:
-//   - cgfnparams: parameter spilling per SysV
-//   - cgfn:       fn body emit (TEXT/SUBQ patched after body), prologue
-//                 deferred via cgen.ww's cgoutstate so the frame size
-//                 reflects every emit-time localadd (#15/#26c)
-//   - cgfile:     file-level entry (the exported driver)
-//
-// Bundler pulls this in transitively via cgen.ww; consumers don't
-// need to `use cgendecl;` directly.
-
 package wcc;
 
 import os;
 import syntax;
 import strconv;
 
-
-// ---- function-level cgen ---------------------------------------------
-
 fn cgfnparams(c: *cgen, params: *syntax.node) void = {
 	let p: *syntax.node = params;
 	// sret (#23): RDI is consumed by the hidden dest pointer
@@ -580,8 +565,6 @@ fn cgfn(c: *cgen, fn_: *syntax.node) void = {
 	};
 
 	if (c.lastwasreturn == 0) {
-		// Run any registered defers in LIFO order before the
-		// implicit return.
 		rundefers(c);
 		// Zero AX before the fall-through return — matches cstage,
 		// which always emits this so void-returning fns don't leak
@@ -629,8 +612,6 @@ fn cgfn(c: *cgen, fn_: *syntax.node) void = {
 	cgout_flush();
 };
 
-// ---- file-level entry ------------------------------------------------
-
 export fn cgfile(c: *cgen, file: *syntax.node) void = {
 	if (file == nil) { return; };
 	c.strlits = nil;