parse,check,type,wwi: @packed struct attribute, both stages (#51)

Hare/harec @packed struct layout: no inter-field or trailing padding, align =
max field align (NOT forced to 1) — matches harec type_store.c + types.c:621
(packed{u8,u64}=size 9/align 8). Parser consumes inline @packed (loud-rejects
unknown struct attrs, both stages); layout gates padding on !packed; cstage
type_eq enforces packed type-distinctness; the .wwi producer round-trips
"struct @packed {". wwstage sets slotsize=size for packed so its composite-ABI
copy matches cstage byte-for-byte. cstage identity is faithful; wwstage identity
rides the deferred #224 nominal-resolvealias arc (#108). Both stages byte-id;
447 tests pass.

lib/ww/syntax/ast.ww

@@ -133,6 +133,7 @@ export type node = struct {
 	next:    *node,
 	attr:    *node,
 	exported: i32,	// bool — `export` keyword present
+	packed:  i32,	// N_TSTRUCT: `struct @packed` — no padding (harec ast.h:95)
 	type_:   *void,	// filled in by checker; type.ww treats it as *tinfo
 	tsuffix: str,	// typed numeric literal suffix ("i32", "u64", ...)
 	nmod:    str,	// originating module from `// MODULE: foo`; "" if none
@@ -146,7 +147,7 @@ export fn newnode(k: nkind, file: str, line: i32, col: i32) *node = {
 	// fval cast-init: 990's wwdump TK_FLOAT diff requires this file
 	// to tokenise identically through C and ww (lex.ww:382 has the
 	// same workaround for the cstage %g-formats vs ww-skips divergence).
-	let n: *node = alloc(node{kind=k, file=file, line=line, col=col, op=tkind.TK_NONE, str="", uval=0u64, fval=0: f64, lhs=nil, rhs=nil, cond=nil, body=nil, els=nil, list=nil, next=nil, attr=nil, exported=0, type_=nil, tsuffix="", nmod="", usepath="", imported=0})!;
+	let n: *node = alloc(node{kind=k, file=file, line=line, col=col, op=tkind.TK_NONE, str="", uval=0u64, fval=0: f64, lhs=nil, rhs=nil, cond=nil, body=nil, els=nil, list=nil, next=nil, attr=nil, exported=0, packed=0, type_=nil, tsuffix="", nmod="", usepath="", imported=0})!;
 	return n;
 };
 

lib/ww/syntax/parse.ww

@@ -191,8 +191,21 @@ fn parsetype(p: *parser) *node = {
 
 	if (p.curkind == tkind.TK_STRUCT) {
 		advance(p);
-		expecttok(p, tkind.TK_LBRACE, "expected '{' after struct");
 		let n = newnode(nkind.N_TSTRUCT, pf, pl, pc);
+		// `@packed` is an inline struct TYPE attribute (harec ast.h:95),
+		// after `struct` and before `{` — NOT a fn-decl attr, so it does
+		// not route through parseattrs.
+		if (p.curkind == tkind.TK_AT) {
+			advance(p);
+			let an: str;
+			expectident(p, &an);
+			if (!streq(an, "packed")) {
+				errmsg(p, "unknown struct attribute");
+			} else {
+				n.packed = 1;
+			};
+		};
+		expecttok(p, tkind.TK_LBRACE, "expected '{' after struct");
 		let fhead: *node = nil;
 		let ftail: *node = nil;
 		for (p.curkind != tkind.TK_RBRACE) {

lib/ww/syntax/typ.ww

@@ -144,6 +144,9 @@ export type tinfo = struct {
 				// still lives at slotsize()'s read site;
 				// graduating it here would break `[N]i32`
 				// stride (4*N stays natural).
+	packed:   i32,	// TY_STRUCT laid out with no padding; part of type
+				// identity (harec types.c:517/621). Mirrors cstage
+				// Type.packed (cmd/wcc/ww.h).
 };
 
 // #61 audit §1.8 / Rob+Drew convergence 2026-05-20: memoizes
@@ -202,7 +205,7 @@ export type tctx = struct {
 // ---- constructors -----------------------------------------------------
 
 export fn newtype(k: tykind) *tinfo = {
-	let t: *tinfo = alloc(tinfo{kind=k, size=0u64, align=0u64, sub=nil, alen=0u64, fields=nil, params=nil, tupleelems=nil, ret=nil, variadic=0, nullable=0, name="", under=nil, slotsize=0u64})!;
+	let t: *tinfo = alloc(tinfo{kind=k, size=0u64, align=0u64, sub=nil, alen=0u64, fields=nil, params=nil, tupleelems=nil, ret=nil, variadic=0, nullable=0, name="", under=nil, slotsize=0u64, packed=0})!;
 	return t;
 };
 
@@ -559,6 +562,9 @@ export fn typeeq(a: *tinfo, b: *tinfo) bool = {
 		return true;
 	};
 	if (k == tykind.TY_STRUCT) {
+		// packed is part of struct identity: a packed struct is not
+		// equal to its unpacked twin (harec types.c:621).
+		if (a.packed != b.packed) { return false; };
 		let fa: *tfield = a.fields;
 		let fb: *tfield = b.fields;
 		for (true) {