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.

lib/path/pathtest.ww

@@ -267,15 +267,3 @@ import path;
 	assert(!(pop(&buf) as str != "foo"));
 	assert(!(string(&buf) != "/"));
 };
-
-export fn main() i32 = {
-	push_cases();
-	isroot_cases();
-	string_cases();
-	dirname_basename_cases();
-	abs_cases();
-	local_cases();
-	parent_cases();
-	popsplit_cases();
-	return 0;
-};