wcc/ww: def-dim array slice-arg default-hi takes the length from the type table

Passing buf[1:] of a [MAX]u8 as a call arg dropped the default-hi
length (the arg-push N_SLICE arms' fallback covered only named-alias
bases). Same type-table resolve at pushargsrev local+global. This
closes the def-dim dimension family by construction: every N_INTLIT-
keyed dim consumer (cgslice, cgdot, letemitsize, arg-push) now
carries the tichase().alen fallback — grep-proven, no consumer
remains. Fourth member surfaced by the family grep.

Makefile

@@ -258,6 +258,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_trystr_run \
 	  $(BIN)/test_allocalias_run \
 	  $(BIN)/test_defdim_field_run \
+	  $(BIN)/test_defdim_argslice_run \
 	  $(BIN)/test_gunsigned_run \
 	  $(BIN)/test_taggedidx_run \
 	  $(BIN)/test_fnptrcollide_run \
@@ -769,6 +770,17 @@ $(BIN)/test_defdim_field_run: test/wcc/989_defdim_field_run.c \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+# 989_defdim_argslice_run (#56 c4): passing a slice of a `def`-dimensioned
+# array as a call arg resolves the default-hi length from the type table in
+# the N_SLICE arg-push arms (cgenutil pushargsrev local+global). Builds+runs
+# on BOTH driver twins (rule-10).
+$(BIN)/test_defdim_argslice_run: test/wcc/989_defdim_argslice_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.