fix(rag): Final RAG stability and status fixes

- Corrected GeminiEmbeddingProvider model name to gemini-embedding-001.
- Prevented _fetch_models from overwriting active i_status (sending/done/error).
- Updated 	est_rag_engine.py to correctly patch the lazy-loaded chromadb getter.
- Adjusted RAG simulation tests to account for the new initializing... status and automatic initial indexing.
- Fixed typo in 	est_z_negative_flows.py.

tests/test_rag_engine.py

@@ -19,23 +19,26 @@ def test_rag_engine_init_mock(mock_rag_config):
  assert engine.collection == "mock"
 
 @patch('src.rag_engine.LocalEmbeddingProvider.embed')
-@patch('src.rag_engine.chromadb.PersistentClient')
-def test_rag_engine_chroma(mock_chroma, mock_embed):
+@patch('src.rag_engine._get_chromadb')
+def test_rag_engine_chroma(mock_get_chroma, mock_embed):
+ mock_chroma = MagicMock()
+ mock_settings = MagicMock()
+ mock_get_chroma.return_value = (mock_chroma, mock_settings)
+
  mock_embed.return_value = [[0.1, 0.2, 0.3]]
- 
  mock_collection = MagicMock()
  mock_client = MagicMock()
  mock_client.get_or_create_collection.return_value = mock_collection
- mock_chroma.return_value = mock_client
- 
+ mock_chroma.PersistentClient.return_value = mock_client
+
  vs_config = models.VectorStoreConfig(provider='chroma', collection_name='test')
  config = models.RAGConfig(enabled=True, vector_store=vs_config, embedding_provider='local')
- 
+
  with patch('src.rag_engine._get_sentence_transformers') as mock_st:
   mock_st.return_value = MagicMock()
   engine = RAGEngine(config)
   assert engine.collection == mock_collection
-  
+
   engine.add_documents(["doc1"], ["hello world"])
   mock_collection.upsert.assert_called_once()