ww test: @test name-filter via fnmatch (both stages)

`ww test <file> <pattern>` runs only the @test fns whose names match the
fnmatch glob; no pattern runs all (byte-for-byte the pre-filter path);
zero matches prints "No tests run" and exits 0 (Hare ground truth
ref/hare/test/+test.ha:114-117). A pattern in directory mode is rejected
"ww test: pattern needs a single test file" (rc 2), identical wording in
both twins (cmd/ww/main.c do_test + selfhost/cmd/ww/main.ww dotest).

Mechanism (a): rt/start.s stashes argc/argv into rt_argc/rt_argv getters
(rt_envp twin shape, -T synth untouched so 990-997 byte-id holds);
lib/os.args() rebuilds the []str view, build-once-cached; lib/test/run.ww
imports fnmatch and filters av[1..] (argv[0] is the binary path). The
driver forwards the 2nd positional as argv[1] via fork/execv (cstage) /
procrun (wwstage) so glob metachars aren't shell-expanded.

os.args() is the first `alloc`-caller in the base os module, so os.ww now
imports rt — the `alloc` builtin's malloc lowers to rt_malloc only when
the rt binding is bundled (mirror lib/strings/strings.ww:30); without it a
plain `ww build` of any os-importing program links bare libc `malloc`
(undefined). os is bundled by ~every program, so this is load-bearing.

The lib/test floor rises os-only -> os+fnmatch+ascii+strings in every -T
build; the bundled `ascii` module vs a `@test fn ascii` collision that
exposed is closed by the preceding #30 promote commit. 989_test_filter
pins the full matrix on both twins byte-identically; 949 gains the
dir-mode reject row. (#17)

lib/getopt/getopt.ww

@@ -229,7 +229,7 @@ fn findflag(hs: []help, r: rune) (helpkind | void) = {
 
 // tryparse — parse `argv` against `help`, filling `*out` on success.
 // `argv` must include the program name in argv[0]; matches Hare and
-// matches the slice [[os.args]] would hand back.
+// matches the slice [[os.args]] hands back.
 //
 // Recognised forms:
 //   -X            FLAG-kind option