feat(bottle): opt-in gVisor runtime per bottle

Bottles can now set "runtime": "runsc" to launch the agent container
under gVisor instead of runc, adding a userspace syscall barrier
between the agent and the host kernel. Default is runc (Docker
default). Pipelock stays on the default runtime per the research doc's
minimum-diff prescription.

The launcher verifies runsc is registered with the daemon before
launch, surfaces the runtime in the preflight plan, and dies with an
install pointer (and a macOS-not-supported note) when runsc is
requested but unavailable.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_dry_run_plan.py

@@ -48,6 +48,7 @@ class TestDryRunPlan(unittest.TestCase):
             # 7 baked defaults + 1 bottle entry = 8.
             self.assertRegex(out, r"8 hosts allowed", "preflight: bottle entry counted")
             self.assertIn("api.anthropic.com", out, "preflight: baked default shown")
+            self.assertRegex(out, r"runtime\s*:\s*runc", "preflight: default runtime shown")
             self.assertIn("dry-run requested", out, "dry-run banner present")
             self.assertNotIn("/dev/tty", out, "dry-run exited before tty prompt")
 

tests/test_manifest_runtime.py

@@ -0,0 +1,49 @@
+"""Unit: manifest_bottle_runtime — defaults to runc, accepts runsc,
+rejects unknown values and non-strings."""
+
+import unittest
+
+from claude_bottle.log import Die
+from claude_bottle.manifest import manifest_bottle_runtime
+
+
+def _bottle(runtime_value: object | None) -> dict:
+    """Build a minimal manifest with one bottle whose runtime field is
+    set (or absent if `runtime_value is _ABSENT`)."""
+    bottle: dict = {}
+    if runtime_value is not _ABSENT:
+        bottle["runtime"] = runtime_value
+    return {
+        "bottles": {"dev": bottle},
+        "agents": {"demo": {"skills": [], "prompt": "", "bottle": "dev"}},
+    }
+
+
+_ABSENT = object()
+
+
+class TestManifestBottleRuntime(unittest.TestCase):
+    def test_default_runc_when_absent(self):
+        self.assertEqual("runc", manifest_bottle_runtime(_bottle(_ABSENT), "dev"))
+
+    def test_explicit_runc(self):
+        self.assertEqual("runc", manifest_bottle_runtime(_bottle("runc"), "dev"))
+
+    def test_explicit_runsc(self):
+        self.assertEqual("runsc", manifest_bottle_runtime(_bottle("runsc"), "dev"))
+
+    def test_rejects_unknown_runtime(self):
+        with self.assertRaises(Die):
+            manifest_bottle_runtime(_bottle("kata-runtime"), "dev")
+
+    def test_rejects_non_string(self):
+        with self.assertRaises(Die):
+            manifest_bottle_runtime(_bottle(42), "dev")
+
+    def test_rejects_empty_string(self):
+        with self.assertRaises(Die):
+            manifest_bottle_runtime(_bottle(""), "dev")
+
+
+if __name__ == "__main__":
+    unittest.main()