w6c/cgen: #71 chained-dot walks chase alias-typed hops — direct offsets, byte-id graduation

rob probe-ruled F1 enrollment (fold-or-file decided by the dispatch
test): the chained-dot STORE walk, its READ twin, and the addr-of
sibling each single-peeled every hop's type, so an alias-typed field
(type fa = inner; outer{x: fa}) aborted the offset-folding fast arm and
fell to the generic address spine — store via cgplaceaddr
(PUSHQ/LEAQ/ADDQ/POPQ), read via ADDQ-per-hop. Runtime-correct BOTH
stages; byte-id NO vs wwstage's folded direct MOVQ offsets
(reviewer-62r diamond find). Chasing the walk hops (+ the read arm's
leaf gate and the two ptr-root sub peels) flips cs onto the fast arm =
wwstage's asm exactly.

Blast radius measured per rob's caution: bootstrap asm cmp-identical
vs the pristine 738d7f4 scratch on all five main.combined.ww, 989
lib_byteid pins unchanged (31/9/3), every control row byte-id — the
flip moves ONLY the #71 shapes.

test: 944_alias_accept_run +2 rows, both decl orders: nested store +
last-field readback; the fwd row adds the &v.y.b addr-of + deref-write
leg. Mutation-checked at the 738d7f4 scratch: both rows byte-id-diff
there; 70/70 green here.

Also graduates the reviewer-F1 slicefield rows: their `.len` readbacks
ride this walk, so the 7 K_RUN_CS rows from commit 1 flip to K_RUN
(byte-id) here.

test/wcc/944_alias_accept_run.c

@@ -50,6 +50,10 @@
  *                        | store/push word0-only; CS-ONLY until |
  *                        | F2 lands the wwstage half; base ctl  |
  *                        | + the #54-bound `as` row pinned loud | 0(cs)
+ *   nested_alias_field_* | task #71: alias-typed nested-field   |
+ *                        | store/read/addr-of walks fold to     |
+ *                        | direct offsets (byte-id graduation,  |
+ *                        | both decl orders)                    | 0
  *
  * K_RUN rows also assert cstage/wwstage asm byte-id (acceptance
  * graduations land byte-identical — F0's accept side was wwstage).
@@ -275,10 +279,9 @@ static const struct row rows[] = {
 	 * noise() call clobbers BX/CX so stale-register luck can't pass a
 	 * word0-only header. Unprobed sibling gates are LOUD-tripwired,
 	 * pinned by the #73 row at the end of this block. Rows whose
-	 * `.len` readback rides the chained-dot READ walk are K_RUN_CS
-	 * here (runtime-correct both stages; cs takes the generic spine
-	 * pre-#71) and flip to K_RUN at the #71 walk-chase commit, which
-	 * graduates their byte-id. */
+	 * `.len` readback rides the chained-dot READ walk entered as
+	 * K_RUN_CS (runtime-correct both stages; cs took the generic
+	 * spine) and graduated to K_RUN with the #71 walk chase. */
 	{ "slicefield_store_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -294,7 +297,7 @@ static const struct row rows[] = {
 	  "	if (b.s[2] != 900) { return 2; };\n"
 	  "	if (b.s.len != 3) { return 3; };\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "slicefield_range_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -311,7 +314,7 @@ static const struct row rows[] = {
 	  "		if (x < 700) { return 3; };\n"
 	  "	};\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "strfield_store_2lvl",
 	  "package main;\n"
 	  "type s1t = str;\n"
@@ -323,7 +326,7 @@ static const struct row rows[] = {
 	  "	b.n = 5;\n"
 	  "	if (b.s.len != 5) { return 1; };\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "slicefield_structlit_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -336,7 +339,7 @@ static const struct row rows[] = {
 	  "	if (b.s.len != 3) { return 2; };\n"
 	  "	if (b.s[2] != 900) { return 3; };\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "slicefield_viaptr_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -350,7 +353,7 @@ static const struct row rows[] = {
 	  "	if (p.s.len != 3) { return 1; };\n"
 	  "	if (p.s[2] != 900) { return 2; };\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "slicefield_chainstore_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -364,7 +367,7 @@ static const struct row rows[] = {
 	  "	if (v.i.s.len != 3) { return 1; };\n"
 	  "	if (v.i.s[2] != 900) { return 2; };\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "slicefield_ptrchain_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -381,7 +384,7 @@ static const struct row rows[] = {
 	  "	if (i.s.len != 3) { return 1; };\n"
 	  "	if (i.s[2] != 900) { return 2; };\n"
 	  "	return 0;\n"
-	  "};\n", 0, K_RUN_CS, NULL },	/* ->K_RUN at the #71 walk-chase commit */
+	  "};\n", 0, K_RUN, NULL },
 	{ "slicefield_chainread_2lvl",
 	  "package main;\n"
 	  "type sl = []int;\n"
@@ -749,6 +752,42 @@ static const struct row rows[] = {
 	  "	};\n"
 	  "	return 0;\n"
 	  "};\n", 0, K_RUN, NULL },
+	/* ---- task #71 (rob probe-ruled F1 enrollment): nested fields
+	 * whose TYPES are aliases. The chained-dot store/read/addr-of
+	 * walks single-peeled each hop, aborted on the alias, and fell
+	 * to the generic PUSHQ/LEAQ/ADDQ/POPQ address spine — runtime-
+	 * correct but byte-id NO vs wwstage's folded direct offsets.
+	 * Chasing the walks converges cs onto the direct arm = ww's asm.
+	 * Distinct values; the LAST field of the SECOND member checked. */
+	{ "nested_alias_field_norm",
+	  "package main;\n"
+	  "type fa = inner;\n"
+	  "type inner = struct { a: size, b: size };\n"
+	  "type outer = struct { x: fa, y: fa };\n"
+	  "export fn main() i32 = {\n"
+	  "	let v: outer;\n"
+	  "	v.x.a = 4; v.x.b = 9;\n"
+	  "	v.y.a = 7; v.y.b = 3;\n"
+	  "	if (v.x.b != 9) { return 1; };\n"
+	  "	if (v.y.b != 3) { return 2; };\n"
+	  "	return 0;\n"
+	  "};\n", 0, K_RUN, NULL },
+	{ "nested_alias_field_fwd",
+	  "package main;\n"
+	  "type outer = struct { x: fa, y: fa };\n"
+	  "type fa = inner;\n"
+	  "type inner = struct { a: size, b: size };\n"
+	  "export fn main() i32 = {\n"
+	  "	let v: outer;\n"
+	  "	v.x.a = 4; v.x.b = 9;\n"
+	  "	v.y.a = 7; v.y.b = 3;\n"
+	  "	if (v.x.b != 9) { return 1; };\n"
+	  "	if (v.y.b != 3) { return 2; };\n"
+	  "	let pa = &v.y.b;\n"
+	  "	*pa = 11;\n"
+	  "	if (v.y.b != 11) { return 3; };\n"
+	  "	return 0;\n"
+	  "};\n", 0, K_RUN, NULL },
 	/* banked row L2-3 (`v as ali` readback) trips task #54's as-binding
 	 * aggregate-init bound — LOUD both stages today; fold the row into
 	 * #54's pin set on its fold (do not drop). Pinned here as the