feat(cli): support conversational AI follow-ups in interactive mode

tests/test_ai.py

@@ -116,6 +116,34 @@ def test_stream_yields_chunks() -> None:
     assert result == ["Root ", "cause ", "found."]
 
 
+def test_stream_messages_yields_chunks() -> None:
+    config = AIConfig()
+    client = AIClient(config)
+
+    def _make_chunk(text: str | None) -> MagicMock:
+        delta = MagicMock()
+        delta.content = text
+        choice = MagicMock()
+        choice.delta = delta
+        chunk = MagicMock()
+        chunk.choices = [choice]
+        return chunk
+
+    mock_chunks = [_make_chunk("A"), _make_chunk(None), _make_chunk("B")]
+
+    with patch.object(client._client.chat.completions, "create", return_value=iter(mock_chunks)):
+        result = list(
+            client.stream_messages(
+                [
+                    {"role": "system", "content": "sys"},
+                    {"role": "user", "content": "question"},
+                ]
+            )
+        )
+
+    assert result == ["A", "B"]
+
+
 # ---------------------------------------------------------------------------
 # prompt_builder
 # ---------------------------------------------------------------------------