feat: better injection, pty snapshots

tests/test_backend.py

@@ -320,10 +320,17 @@ async def test_unmatched_history_spawns_new_session_via_native_jsonl(
     seed_lines = [
         json.loads(line) for line in seed_bytes.decode("utf-8").strip().splitlines()
     ]
-    # Two seeded records (one user + one assistant) for the prior turn.
-    assert [r["type"] for r in seed_lines] == ["user", "assistant"]
-    assert seed_lines[0]["message"]["content"] == "remember beaver"
-    assert seed_lines[1]["message"]["content"] == [{"type": "text", "text": "ok"}]
+    # Seeded prior turn: permission-mode + snapshot + user + assistant.
+    assert [r["type"] for r in seed_lines] == [
+        "permission-mode",
+        "file-history-snapshot",
+        "user",
+        "assistant",
+    ]
+    user_rec = seed_lines[2]
+    asst_rec = seed_lines[3]
+    assert user_rec["message"]["content"] == "remember beaver"
+    assert asst_rec["message"]["content"] == [{"type": "text", "text": "ok"}]
     assert isinstance(events[-1], ResultMessage)