ww: lib tests run via -T test mode; bare mains retired (closes @test conversion)

'ww test' gains the istest build path (-T injection in build_one/
buildone) and do_test/dotest accept -I, mirroring do_run - both twins.
The 35 converted lib tests drop their interim bare mains (-T
synthesizes the entry from @test fns and rejects a user main); their
35 C run-drivers flip 'ww run' -> 'ww test'; 989_lib_byteid compiles
lib tests under -T (8 user-main probe fixtures stay non-T, gated on
the fixture field). Abort-on-first-failure stands until the deferred
record-and-continue harness lands with the multi-package arc.

test/wcc/989_regex_run.c

@@ -47,7 +47,7 @@ main(void)
 	 * regression of the ha:946-952 rune-advancement guard into an
 	 * infinite loop (frees are no-ops, so OOM is the only other
 	 * exit) — timeout converts the hang into a loud 124. */
-	snprintf(cmd, sizeof cmd, "timeout 180 %s/ww run %s", bin, path);
+	snprintf(cmd, sizeof cmd, "timeout 180 %s/ww test %s", bin, path);
 	int rc = runwait(cmd);
 	if (rc != 0) {
 		fprintf(stderr, "regex_run FAIL: %s exited %d\n", src, rc);