wcc+w6c_ww: cgplaceaddr resolver — deref-base assign stores (F6)

(*ts)[i].field = v / OP= v (the regex run_thread hot shape, task #4)
compiled to NOTHING in both stages, byte-identically: the N_DOT lhs
roots at N_UN(STAR), so the arr[i].field arm (idxbase must be IDENT)
and the chained-ptr-field arm (base must be *struct) both miss and
the N_ASSIGN dispatch fell off the switch silently, rhs unevaluated.

cgplaceaddr (one per stage) is ADDRESS COMPUTATION ONLY — N_UN(STAR)
root, N_INDEX hop over a slice/array place (.ptr hop for slice),
N_DOT struct-field hop with one deref for a *struct base. Call-sites
keep their own emission: scalar fldstoreop store, str/slice 3-word
header store staged through DX, 10-op compound template with the
chained-ptr-field register roles. Ident-rooted spines stay with the
enumerated arms — verified asm-neutral over the 84 fold2b probe
sources against fresh master-HEAD binaries (7 diffs = the F6 family
now emitting stores; 2 verdict flips = aggregate-field stores, now
loud).

Silent dispatch tails go LOUD for N_DOT lvalues the resolver can't
address and for unresolved-identifier targets (cstage float-ident arm
aligned to wwstage's resolve-first order). Aggregate-field stores
loud-reject pending the follow-up resolver commit (task #23, ≤24B
N_CALL rhs split to #24). The non-DOT tail stays silent deliberately:
going loud there would asymmetrically surface the pre-existing
str-base element-store divergence — task #22, cited at both sites.

test/805: 17 rows x 2 drivers + 12 cs==ww byte-id fixtures — widths
(incl narrow-compound fldloadop sign/zero-extension), all 10 compound
ops (DIVQ/IDIVQ/SHLQ/SARQ/SHRQ), str + slice 3-word stores, *[N]T
base, runtime call index, ident-base neutrality pins, and 5 reject
rows asserting exact diagnostic text.

Makefile

@@ -389,6 +389,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_tuple_sret_receive_run \
 	  $(BIN)/test_append_wide_elem \
 	  $(BIN)/test_delete_elem \
+	  $(BIN)/test_placeaddr_store \
 	  $(BIN)/test_struct_tuple_field_slot \
 	  $(BIN)/test_widen_pad_zero_run \
 	  $(BIN)/test_named_ptr_alias_variant_widen \
@@ -1011,6 +1012,16 @@ $(BIN)/test_delete_elem: test/wcc/804_delete_elem.c \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+# F6 (task #4, regex fold-2b): (*ts)[i].field = v / OP= v through the
+# cgplaceaddr resolver — runtime rows across widths/signedness/str +
+# compound ops + loud-tail reject rows w/ exact diagnostic text + cs==ww
+# asm byte-id.
+$(BIN)/test_placeaddr_store: test/wcc/805_placeaddr_store.c \
+		$(BIN)/ww $(BIN)/w6c $(BIN)/w6c_ww $(BIN)/w6a $(BIN)/w6l \
+		$(BIN)/ww_ww \
+		$(LIB)/libwwrt.a | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 # #237: a tuple-typed struct field must contribute its real slot width to
 # the enclosing struct's slotsize — pure cs==ww .s byte-id (frame size).
 $(BIN)/test_struct_tuple_field_slot: test/wcc/930_struct_tuple_field_slot.c \