fix: Add cosine distance metric to remaining collection creation calls

- Fix all create_collection calls to use distance_metric='cosine'
- Includes exception handlers and error recovery paths
- Ensures all new collections use cosine distance for normalized embeddings

Author: anhmtk

stillme_core/rag/chroma_client.py

@@ -258,7 +258,9 @@ def __init__(self, persist_directory: str = None, reset_on_error: bool = False,
                             pass
                         self.knowledge_collection = self.client.create_collection(
                             name="stillme_knowledge",
-                            metadata={"description": "Knowledge base for StillMe learning"}
+                            metadata={"description": "Knowledge base for StillMe learning"},
+                            # CRITICAL: Use cosine distance for normalized embeddings
+                            distance_metric="cosine"
                         )
                     else:
                         raise
@@ -282,7 +284,9 @@ def __init__(self, persist_directory: str = None, reset_on_error: bool = False,
                             pass
                         self.conversation_collection = self.client.create_collection(
                             name="stillme_conversations",
-                            metadata={"description": "Conversation history for context"}
+                            metadata={"description": "Conversation history for context"},
+                            # CRITICAL: Use cosine distance for normalized embeddings
+                            distance_metric="cosine"
                         )
                     else:
                         raise
@@ -526,11 +530,15 @@ def __init__(self, persist_directory: str = None, reset_on_error: bool = False,
                         # Create fresh collections
                         self.knowledge_collection = self.client.create_collection(
                             name="stillme_knowledge",
-                            metadata={"description": "Knowledge base for StillMe learning"}
+                            metadata={"description": "Knowledge base for StillMe learning"},
+                            # CRITICAL: Use cosine distance for normalized embeddings
+                            distance_metric="cosine"
                         )
                         self.conversation_collection = self.client.create_collection(
                             name="stillme_conversations",
-                            metadata={"description": "Conversation history for context"}
+                            metadata={"description": "Conversation history for context"},
+                            # CRITICAL: Use cosine distance for normalized embeddings
+                            distance_metric="cosine"
                         )
                         logger.info("✅ ChromaDB database reset successfully - fresh collections created")
                     except Exception as reset_error: