test: port 989_lib_byteid to ww; birth test/testenv + test/byteid

test/testenv (package testenv) is the shared plumbing for ww-native
test drivers — subprocess launch with captured output, file IO, string
search, byte-sorted directory listing, scratch ownership — lifted from
the proven package_test.ww idiom; a utility, not a framework.

test/byteid/libbyteid_test.ww carries every assertion of the retired C
carrier: the 44-entry roster (fixtures + sentinel-guarded import probes
+ the zero-dep root-only build), both-stage sep builds with the
resolved-unit proof, per-package .s concat compare with the empty-concat
guard, the ID/DIVERGE/WWREJECT pin discipline, and the lib/ corpus
completeness scan (negative-verified against a planted un-enrolled
module). Concat order strengthened from shell-glob to explicit
byte-lexicographic. The roster fills by cursor-driven field writes
because append() rejects struct-call-result sources (#34).

Byteid carriers 11 -> 10; docs counts move; test-byteid runs the ww
test via the wwtest/ pattern with WW_TEST_REPO.

Makefile

@@ -356,7 +356,14 @@ BYTEID_WRAPPER_SOURCES = test/wcc/753_convwrap_audit.c \
 	  test/wcc/946_structret_run.c \
 	  test/wcc/989_m1mangle_sym.c \
 	  test/wcc/989_m2wwi_run.c \
-	  test/wcc/989_wwileaf_run.c test/wcc/989_lib_byteid.c
+	  test/wcc/989_wwileaf_run.c
+
+# Ww-native byte/artifact observers: single-file ww tests under
+# test/byteid/ on the test/testenv helper package. Each drives both
+# driver stages itself, so the build needs only cstage plus the two
+# stage frontends it launches.
+BYTEID_WW_TESTS = test/byteid/libbyteid_test.ww
+BYTEID_WW_TARGETS = $(BYTEID_WW_TESTS:%=wwtest/%)
 BOOTSTRAP_WRAPPER_SOURCES = test/wcc/950_selfcheck.c \
 	  test/wcc/991_w6a_ww.c \
 	  test/wcc/992_w6l_ww.c test/wcc/993_ww_ww.c \
@@ -455,6 +462,14 @@ $(LIBRARY_TEST_TARGETS): wwtest/%: $(BIN)/ww \
 	@$(BIN)/ww test -w $(WWBUILD)/wwtest/$(subst /,_,$*) \
 		-I $(CURDIR)/lib/ww $*
 
+$(BYTEID_WW_TARGETS): wwtest/%: $(BIN)/ww $(BIN)/w6c $(BIN)/w6a \
+		$(BIN)/w6l $(LIB)/libwwrt.a $(BIN)/ww_ww $(BIN)/w6c_ww
+	@echo "ww test $*"
+	@mkdir -p $(WWBUILD)/wwtest/$(subst /,_,$*)
+	@WW_TEST_REPO=$(CURDIR) $(BIN)/ww test \
+		-w $(WWBUILD)/wwtest/$(subst /,_,$*) \
+		-I $(CURDIR)/test $*
+
 test-lang: $(LANG_TEST_TARGETS)
 
 test-library: $(LIBRARY_TEST_TARGETS) $(BIN)/w6c $(BIN)/w6c_ww \
@@ -617,7 +632,8 @@ test-data-byteid: $(BIN)/ww $(BIN)/w6c $(BIN)/w6c_ww
 	fi; \
 	exit $$rc
 
-test-byteid: test-lang-byteid test-data-byteid test-native-byteid
+test-byteid: test-lang-byteid test-data-byteid test-native-byteid \
+	$(BYTEID_WW_TARGETS)
 
 # Incremental == clean. The -w reuse path must be byte-identical to a
 # from-scratch build, or it is not a build-graph optimization but a
@@ -821,7 +837,7 @@ nocc:
 .PHONY: all cstage wwstage wwfixture test-wwfixture-process test-wwfixture \
 	test test-unit test-compiler-smoke test-compiler test-package \
 	test-lang test-library test-commit test-lang-byteid \
-	$(LANG_TEST_TARGETS) $(LIBRARY_TEST_TARGETS) \
+	$(LANG_TEST_TARGETS) $(LIBRARY_TEST_TARGETS) $(BYTEID_WW_TARGETS) \
 	test-data-byteid test-native-byteid test-byteid \
 	test-bootstrap-native test-bootstrap test-incremental \
 	test-platform test-all install clean bootstrap nocc bootstrap-snapshot