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single-PT_LOAD and no-archive claims, superseded ABI tables); every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/w6a/asm.ww

@@ -1,13 +1,5 @@
-// selfhost/cmd/w6a/asm.ww — port of cmd/w6a/asm.c.
-//
-// Encode the parsed aprog list into amd64 machine bytes, appending to
-// asm_.text. Relocations for CALL/branch targets that resolve to
-// externals are queued in asm_.relocs.
-//
-// Encoding subset matches what w6c emits — see cmd/w6a/asm.c for the
-// authoritative list. Helpers (rcode/rhi/modrm/emitrex etc.) are
-// fully ported; encode itself is still a stub pending the full
-// switch over A_*.
+// Port of cmd/w6a/asm.c. Encoding subset matches what w6c emits — see
+// cmd/w6a/asm.c for the authoritative list.
 
 package w6a;
 
@@ -16,8 +8,6 @@ import rt;
 import opcodes;
 import strings;
 
-// ---- text buffer growth ------------------------------------------------
-
 export fn emitbyte(a: *asm_, b: u8) void = {
 	if (a.textlen + 1u64 > a.textcap) {
 		let nc: u64 = a.textcap;
@@ -45,16 +35,14 @@ export fn addreloc(a: *asm_, off: u64, kind: i32, s: *asym, add: i64) void = {
 	a.relocs = r;
 };
 
-// Record a relocation that lives in the .data section. Used by
-// DATAR to patch a 64-bit slot with a symbol's runtime VA. obj.ww
-// separates these into .rela.data when emitting the .o.
+// DATAR patches a 64-bit .data slot with a symbol's runtime VA;
+// obj.ww separates section=1 relocs into .rela.data when emitting
+// the .o.
 export fn addrelocdata(a: *asm_, off: u64, kind: i32, s: *asym, add: i64) void = {
 	let r: *areloc = alloc(areloc { off = off, section = 1, kind = kind, asy = s, addend = add, rnext = a.relocs })!;
 	a.relocs = r;
 };
 
-// Append one byte to the writable .data buffer. Mirrors emitbyte
-// but targets a.data instead of a.text.
 export fn emitdatabyte(a: *asm_, b: u8) void = {
 	if (a.datalen + 1u64 > a.datacap) {
 		let nc: u64 = a.datacap;
@@ -70,8 +58,6 @@ export fn emitdatabyte(a: *asm_, b: u8) void = {
 	a.datalen += 1u64;
 };
 
-// ---- register codes ----------------------------------------------------
-
 // Low 3 bits of register encoding.
 fn rcode(r: i32) i32 = {
 	if (r == D_AX) { return 0; };  if (r == D_CX) { return 1; };
@@ -105,7 +91,6 @@ fn isxmm(r: i32) bool = {
 	return false;
 };
 
-// ModR/M byte builder.
 fn modrmbyte(mod: i32, reg: i32, rm: i32) u8 = {
 	return (((mod & 3) << 6) | ((reg & 7) << 3) | (rm & 7)): u8;
 };
@@ -210,8 +195,6 @@ fn sserrw(a: *asm_, prefix: u8, op2: u8, regop: i32, rmop: i32) void = {
 	emitbyte(a, modrmbyte(3, rcode(regop), rcode(rmop)));
 };
 
-// ---- label resolution / fixups ----------------------------------------
-
 fn resolvelabel(a: *asm_, name: str) u64 = {
 	let s: *asym = a.syms;
 	for (s != nil) {
@@ -230,8 +213,6 @@ fn labeldefined(a: *asm_, name: str) bool = {
 	return false;
 };
 
-// ---- fixup helper -----------------------------------------------------
-
 fn addfixup(a: *asm_, off: u64, label: str) void = {
 	let f: *afixup = alloc(afixup { off = off, label = label, fnext = a.fixups })!;
 	a.fixups = f;
@@ -242,15 +223,9 @@ fn isgpr(t: i32) bool = {
 	return false;
 };
 
-// `intern` lives in parse.ww — flat-scope concat lets us call it
-// directly without an @symbol declaration here.
-
-// ---- encode ----------------------------------------------------------
-
 export fn encode(a: *asm_) i32 = {
 	let p: *aprog = a.head;
 	for (p != nil) {
-		// Define any pending label at the current PC.
 		if (p.label.len > 0) {
 			let s: *asym = intern(a, p.label);
 			s.defined = 1;
@@ -281,10 +256,9 @@ export fn encode(a: *asm_) i32 = {
 			p = p.link; continue;
 		};
 		if (op == A_DATAW) {
-			// Writable variant: bytes go into .data instead of
-			// .text. obj.ww emits the extra section conditionally
-			// on datalen > 0 so .o output stays byte-identical
-			// for inputs that don't use DATAW.
+			// obj.ww emits the .data section conditionally on
+			// datalen > 0 so .o output stays byte-identical for
+			// inputs that don't use DATAW.
 			let s: *asym = intern(a, p.to.asym);
 			s.defined = 1;
 			s.isdata = 1;