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/strings/stringstest.ww

@@ -1671,52 +1671,3 @@ fn expect_str(toks: []str, i: i32, want: str) void = {
 	assert(!(!streq(a7, "abc")));
 	assert(!(!streq(b7, "")));
 };
-
-export fn main() i32 = {
-	dup_cases();
-	dupall_cases();
-	concat_cases();
-	join_cases();
-	hasprefix_cases();
-	hassuffix_cases();
-	contains_cases();
-	byteindex_str_cases();
-	byteindex_rune_cases();
-	rbyteindex_cases();
-	index_cases();
-	rindex_cases();
-	trimprefix_cases();
-	trimsuffix_cases();
-	ltrim_cases();
-	rtrim_cases();
-	trim_cases();
-	compare_cases();
-	sub_cases();
-	bytesub_cases();
-	utf8_roundtrip_cases();
-	iter_empty_cases();
-	iter_ascii_cases();
-	iter_twobyte_cases();
-	iter_threebyte_cases();
-	iter_fourbyte_cases();
-	iter_mixed_cases();
-	iter_prev_at_start_cases();
-	iter_prev_ascii_cases();
-	iter_full_cases();
-	iter_position_cases();
-	iter_iterstr_reverse_cases();
-	iter_slice_cases();
-	tokenize_cases();
-	rtokenize_cases();
-	peek_token_cases();
-	remaining_tokens_cases();
-	splitn_cases();
-	rsplitn_cases();
-	split_cases();
-	lpad_cases();
-	rpad_cases();
-	replace_cases();
-	cut_cases();
-	rcut_cases();
-	return 0;
-};