wcc/ww: alloc of an alias struct literal chases the alias for size and fill

alloc(alias{...}) keyed the size and field-fill off the syntactic
alias name — it under-allocated and emitted zero field stores. Chase
the alias via structlookupchain to the resolved struct (depth-2
chains verified). The scalar else-branch keeps its pre-existing
benign cs!=ww divergence, surfaced here and deferred as task #57
(site note at the arm). Review item #26.

Makefile

@@ -256,6 +256,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_arrlit_tail_zero_run \
 	  $(BIN)/test_defdim_slice_run \
 	  $(BIN)/test_trystr_run \
+	  $(BIN)/test_allocalias_run \
 	  $(BIN)/test_gunsigned_run \
 	  $(BIN)/test_taggedidx_run \
 	  $(BIN)/test_fnptrcollide_run \
@@ -746,6 +747,16 @@ $(BIN)/test_trystr_run: test/wcc/989_trystr_run.c \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+# 989_allocalias_run (#26): alloc(T{...}) for an alias T sizes + field-fills
+# from the alias-chased struct layout, not a name-keyed lookup of the literal
+# head. Builds+runs on BOTH driver twins (rule-10).
+$(BIN)/test_allocalias_run: test/wcc/989_allocalias_run.c \
+		$(BIN)/ww $(BIN)/ww_ww \
+		$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
+		$(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
+		$(LIB)/libwwrt.a | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 # 989_gunsigned_run (F7-c5, #25): a module-global unsigned ident on the
 # divide/shift/relational path must pick the unsigned opcode. Builds+runs on
 # BOTH driver twins (rule-10). CLASS-M — see the test header.