wcc/ww: paramfieldsize sizes a tagged-union destructure binding

A tagged for-range destructure binding took the 8-byte default
(paramfieldsize had no tagged arm), skipping the full-extent copy —
the wwstage twin of the just-closed cstage destructure family. Read
the stamped tinfo size through the type table (twin of the slice
arm; cstage reads tp->type->size). Task #53.

selfhost/cmd/w6c/main.combined.ww

@@ -39221,6 +39221,22 @@ fn paramfieldsize(t: *node) i32 = {
 	// tyslicesize() is the slice-header SSoT (rule-13); cstage reads the
 	// same width via tp->type->size (cmd/w6c/cgen.c N_FORRANGE).
 	if (k == nkind.N_TSLICE) { return tyslicesize(): i32; };
+	// #53: a tagged-union tuple-field carries its full box (tag + widest
+	// payload, slot-padded), NOT the 8B scalar default — a for-range
+	// destructure binding sized 8 loaded only the tag word (cs=56/ww=9, the
+	// cat-A repro). The box width is variant-dependent, so read it from the
+	// checker-stamped tinfo (rule-13): cstage's tp->type->size reads the same
+	// resolved width. The stamp already collapsed any alias, so this also
+	// covers an N_TNAME field naming a tagged union (paramfieldsize's no-`c`
+	// structural contract can't aliaslookup-chase the node). Mirrors the
+	// N_TSLICE arm's type-table SSoT.
+	let tgi: *tinfo = t.type_: *tinfo;
+	if (tgi != nil) {
+		tgi = tichase(tgi);
+		if (tgi != nil && tgi.kind == tykind.TY_TAGGED) {
+			return tgi.size: i32;
+		};
+	};
 	// #43 (F7-c4): a nested tuple field sizes as the sum of its element
 	// SLOTS — each element floored UP to one 8B eightbyte (str/slice keep
 	// their 24B header), per the tuple-slot ruling and tupeslot's

selfhost/cmd/wcc/cgenstmt.ww

@@ -3669,6 +3669,22 @@ fn paramfieldsize(t: *node) i32 = {
 	// tyslicesize() is the slice-header SSoT (rule-13); cstage reads the
 	// same width via tp->type->size (cmd/w6c/cgen.c N_FORRANGE).
 	if (k == nkind.N_TSLICE) { return tyslicesize(): i32; };
+	// #53: a tagged-union tuple-field carries its full box (tag + widest
+	// payload, slot-padded), NOT the 8B scalar default — a for-range
+	// destructure binding sized 8 loaded only the tag word (cs=56/ww=9, the
+	// cat-A repro). The box width is variant-dependent, so read it from the
+	// checker-stamped tinfo (rule-13): cstage's tp->type->size reads the same
+	// resolved width. The stamp already collapsed any alias, so this also
+	// covers an N_TNAME field naming a tagged union (paramfieldsize's no-`c`
+	// structural contract can't aliaslookup-chase the node). Mirrors the
+	// N_TSLICE arm's type-table SSoT.
+	let tgi: *tinfo = t.type_: *tinfo;
+	if (tgi != nil) {
+		tgi = tichase(tgi);
+		if (tgi != nil && tgi.kind == tykind.TY_TAGGED) {
+			return tgi.size: i32;
+		};
+	};
 	// #43 (F7-c4): a nested tuple field sizes as the sum of its element
 	// SLOTS — each element floored UP to one 8B eightbyte (str/slice keep
 	// their 24B header), per the tuple-slot ruling and tupeslot's

selfhost/cmd/wwdump/main.combined.ww

@@ -39221,6 +39221,22 @@ fn paramfieldsize(t: *node) i32 = {
 	// tyslicesize() is the slice-header SSoT (rule-13); cstage reads the
 	// same width via tp->type->size (cmd/w6c/cgen.c N_FORRANGE).
 	if (k == nkind.N_TSLICE) { return tyslicesize(): i32; };
+	// #53: a tagged-union tuple-field carries its full box (tag + widest
+	// payload, slot-padded), NOT the 8B scalar default — a for-range
+	// destructure binding sized 8 loaded only the tag word (cs=56/ww=9, the
+	// cat-A repro). The box width is variant-dependent, so read it from the
+	// checker-stamped tinfo (rule-13): cstage's tp->type->size reads the same
+	// resolved width. The stamp already collapsed any alias, so this also
+	// covers an N_TNAME field naming a tagged union (paramfieldsize's no-`c`
+	// structural contract can't aliaslookup-chase the node). Mirrors the
+	// N_TSLICE arm's type-table SSoT.
+	let tgi: *tinfo = t.type_: *tinfo;
+	if (tgi != nil) {
+		tgi = tichase(tgi);
+		if (tgi != nil && tgi.kind == tykind.TY_TAGGED) {
+			return tgi.size: i32;
+		};
+	};
 	// #43 (F7-c4): a nested tuple field sizes as the sum of its element
 	// SLOTS — each element floored UP to one 8B eightbyte (str/slice keep
 	// their 24B header), per the tuple-slot ruling and tupeslot's