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/strconv/test/inttest.ww

@@ -296,17 +296,3 @@ fn cks(id: i32, got: str, want: str) void = {
 	cks(99, i32tos(-2147483648i32, base.DEC), "-2147483648");
 	cks(100, u8tos(255u8, base.HEX_LOWER), "ff");
 };
-
-export fn main() i32 = {
-	test_stoi64();
-	test_stoi64_bases();
-	test_stou64();
-	test_stou64_bases();
-	test_stoi_stou_stoz();
-	test_u64tos_bases();
-	test_u64tos();
-	test_i64tos_bases();
-	test_i64tos();
-	test_word_wrappers();
-	return 0;
-};