test/package: wire the runtime fixture set into package_test

test/package/runtime/ was a manual README-driven corpus with no
target. Its unique surface — the driver's single-file ww test leg,
the unmet-expected-abort outcome, and the published -c binary's own
CLI (repeated globs, -list, -timeout-ms, direct-binary timeout and
descendant handling) — is now asserted by three new @test fns in
package_test.ww; the README drops its manual-run instructions.

test/package/runtime/README.md

@@ -1,45 +1,23 @@
-# Native package-runtime fixtures
+# Package-runtime fixtures
 
-These fixtures exercise the compiled package test binary, rather than a
-subprocess-per-assertion harness. Build the bootstrap tools once with `make all`,
-then run the focused cases from the repository root:
+Single-file `@test` sources driven by `test/package/package_test.ww`
+(the `make test-package` binary): `singlefile_runtime_outcomes`,
+`published_binary_cli`, and `direct_binary_timeout_and_descendants`.
+They exercise the driver's single-file `ww test` leg and the published
+`-c` binary's own command surface (repeated globs, `-list`,
+`-timeout-ms`); the directory-package legs of the same outcome classes
+are owned by `test/package/cases/*`.
 
-```sh
-out/bin/ww test test/package/runtime/success_test.ww
-out/bin/ww test -c -o /tmp/ww-runtime-test test/package/runtime/success_test.ww
-/tmp/ww-runtime-test 'alpha*' 'delta*'
-/tmp/ww-runtime-test -list
-/tmp/ww-runtime-test -list 'gamma*'
-/tmp/ww-runtime-test -timeout-ms=50 'alpha*'
-out/bin/ww test test/package/runtime/fail_test.ww
-out/bin/ww test test/package/runtime/multiple_fail_test.ww
-out/bin/ww test test/package/runtime/expected_abort_return_test.ww
-out/bin/ww test test/package/runtime/premature_exit_test.ww
-out/bin/ww test test/package/runtime/signal_test.ww
-out/bin/ww test -c -o /tmp/ww-runtime-timeout test/package/runtime/timeout_test.ww
-/tmp/ww-runtime-timeout -timeout-ms=50
-out/bin/ww test -c -o /tmp/ww-runtime-descendant test/package/runtime/lingering_descendant_test.ww
-/tmp/ww-runtime-descendant -timeout-ms=250
-out/bin/ww test -c -o /tmp/ww-runtime-escaped test/package/runtime/escaped_descendant_test.ww
-/tmp/ww-runtime-escaped -timeout-ms=250
-```
+Fixture notes:
 
-The success fixture reports two ordinary passes, one expected-abort pass, and
-one skip with its reason. The preserved test binary accepts repeated glob
-arguments directly. List mode prints selected names without starting tests.
-Each test has a 30-second default timeout; `-timeout-ms=N` selects a positive
-per-test timeout up to one hour for a direct test-binary invocation.
-The current runtime recognizes `expectabort(); os.exit(nonzero)` as an expected
-abort because WW's abort primitive itself terminates with a normal exit status;
-the ABI cannot distinguish those two paths without a future abort hook.
-The assertion, multiple-failure, unmet-expected-abort, premature-exit, and
-signal fixtures fail respectively with a normal exit, two failures whose
-process status is still clamped to 1, an expected abort that never happens, an
-incomplete completion record, and signal 15; none may be mistaken for a pass.
-The timeout fixture fails deterministically as `FAIL(timeout)`. The lingering
-descendant fixture passes without waiting on the inherited control-pipe writer:
-the descendant blocks SIGTERM, so the runner exercises its grace period and
-SIGKILL escalation before draining the record.
-The escaped-descendant fixture moves its inherited writer into another process
-group for one second. The framed nonblocking protocol returns immediately after
-the test leader and owned group complete; it never waits for pipe EOF.
+- The runtime recognizes `expectabort(); os.exit(nonzero)` as an
+  expected abort because WW's abort primitive itself terminates with a
+  normal exit status; the ABI cannot distinguish those two paths
+  without a future abort hook.
+- The lingering-descendant fixture blocks SIGTERM in its descendant, so
+  the runner exercises its grace period and SIGKILL escalation before
+  draining the record.
+- The escaped-descendant fixture moves its inherited pipe writer into
+  another process group for one second; the framed nonblocking protocol
+  must return after the test leader and owned group complete, never
+  waiting for pipe EOF.