fix: isolate rein results and normalize manager startup failures

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a0726e-5232-73f2-aaca-2c05ceb62efb

tests/test_gateway.py

@@ -401,3 +401,17 @@ def test_teardown_failure_is_visible_in_evidence() -> None:
     assert result.evidence.failure_stage == "teardown"
     assert result.evidence.error == "teardown failed; inspect direct caller error"
     assert result.tool_error == "cannot teardown"
+
+
+def test_manager_initialization_failure_returns_redacted_evidence():
+    with patch("glas_harness.gateway.SandboxManager", side_effect=RuntimeError(
+        "private manager configuration"
+    )), patch("glas_harness.gateway.hub.post_progress_event") as post:
+        result = run_execution(_request(report_to_hub=True),
+                               catalog=_catalog_with_readiness(), rein=_FakeRein())
+    assert not result.ok
+    assert result.evidence.failure_stage == "sandbox_create"
+    assert result.evidence.sandbox_id is None
+    assert result.tool_error == "private manager configuration"
+    assert "private manager configuration" not in str(post.call_args)
+    post.assert_called_once()