fix(runtime): fold native execution into shared containment (ODY-152)

tests/containment_helpers.py

@@ -0,0 +1,31 @@
+"""Captured spawns exercise the production runner without signalling fake PIDs."""
+import asyncio
+from types import SimpleNamespace
+
+from src import containment
+
+
+def capture_owned_spawn(monkeypatch, tmp_path):
+    captured = {}
+    monkeypatch.setattr(containment, "CONTAINMENT_MODE", containment.MODE_REPORT_ONLY)
+    monkeypatch.setattr(containment, "_store_path", lambda: tmp_path / "grants.json")
+    monkeypatch.setattr(containment, "_pgid_of", lambda pid: pid)
+
+    async def fake_exec(*argv, **kwargs):
+        captured.update(argv=argv, kwargs=kwargs, command=argv[-1])
+        stdout = asyncio.StreamReader()
+        stdout.feed_data(b"ok")
+        stdout.feed_eof()
+        stderr = asyncio.StreamReader()
+        stderr.feed_eof()
+        async def wait():
+            return 0
+        return SimpleNamespace(pid=99999999, stdout=stdout, stderr=stderr,
+                               returncode=0, wait=wait)
+
+    async def release(*args, **kwargs):
+        return containment.ReleaseOutcome(dead=True, escalated=False)
+
+    monkeypatch.setattr(asyncio, "create_subprocess_exec", fake_exec)
+    monkeypatch.setattr(containment, "_release_awaited", release)
+    return captured