fix: propagate AddResult failures and log embedding errors (#2821)

- knowledge.py: Check AddResult.success before appending ID to results;
  log warning when embedding/storage fails instead of silently counting
  failed chunks as successes
- factories.py: Log embedding exceptions at WARNING level in both
  ChromaKnowledgeAdapter.add() and .search() instead of silently
  swallowing them

This fixes the issue where `praisonai index` reports success but Chroma
stays empty when embedding fails, and where `praisonai search` returns
empty results with no explanation.

src/praisonai-agents/praisonaiagents/knowledge/adapters/factories.py

@@ -151,7 +151,8 @@ class ChromaKnowledgeAdapter:
             query_embedding = result.embeddings[0] if result.embeddings else None
         except Exception as e:
             logger.warning(
-                "Embedding failed for search query (model=%s): %s", embedding_model, e
+                "Embedding failed for search query (model=%s): %s", embedding_model, e,
+                exc_info=True
             )
             query_embedding = None
         
@@ -233,7 +234,8 @@ class ChromaKnowledgeAdapter:
             content_embedding = result.embeddings[0] if result.embeddings else None
         except Exception as e:
             logger.warning(
-                "Embedding failed for add (model=%s): %s", embedding_model, e
+                "Embedding failed for add (model=%s): %s", embedding_model, e,
+                exc_info=True
             )
             embedding_error = e
             content_embedding = None