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/fmt/fmttest.ww

@@ -631,50 +631,3 @@ fn errsource() io.stream = {
 	assert(!(!streq(r, "1.5 -2.5")));
 	os.free(r.ptr: *void, r.len: u64);
 };
-
-export fn main() i32 = {
-	fprintbarestr();
-	fprintintstr();
-	fprintboolrune();
-	fprintempty();
-	fprintlnmulti();
-	fprintlnempty();
-	fprintfixedshort();
-	fprintclosed();
-	fprintf_implicit();
-	fprintf_indexed();
-	fprintf_literal_braces();
-	fprintf_width_right();
-	fprintf_width_left();
-	fprintf_width_center();
-	fprintf_pad_underscore();
-	fprintf_base_hex();
-	fprintf_base_oct_bin();
-	fprintf_prec_int();
-	fprintf_prec_str_trunc();
-	fprintf_sign_neg();
-	fprintfln_basic();
-	fprintf_closed();
-	bsprintf_basic();
-	fprintf_bool_rune();
-	bsprintf_trunc();
-	bsprintf_width_trunc();
-	asprintf_basic();
-	asprintf_growth();
-	asprintf_empty();
-	asprintf_indexed_mods();
-	fprintf_f64_basic();
-	fprintf_f64_int_valued();
-	fprintf_f64_neg();
-	fprintf_f64_zero();
-	fprintf_f64_small_frac();
-	fprintf_f64_huge();
-	fprintf_f64_sign_plus();
-	fprintf_f64_sign_space();
-	fprintf_f64_width_right();
-	fprintf_f64_width_left();
-	fprint_f64_variadic();
-	bsprintf_f64();
-	asprintf_f64();
-	return 0;
-};