Deliver explainability triples inline in retrieval response stream (#763)

Provenance triples are now included directly in explain messages from
GraphRAG, DocumentRAG, and Agent services, eliminating the need for
follow-up knowledge graph queries to retrieve explainability details.

Each explain message in the response stream now carries:
- explain_id: root URI for this provenance step (unchanged)
- explain_graph: named graph where triples are stored (unchanged)
- explain_triples: the actual provenance triples for this step (new)

Changes across the stack:
- Schema: added explain_triples field to GraphRagResponse,
  DocumentRagResponse, and AgentResponse
- Services: all explain message call sites pass triples through
  (graph_rag, document_rag, agent react, agent orchestrator)
- Translators: encode explain_triples via TripleTranslator for
  gateway wire format
- Python SDK: ProvenanceEvent now includes parsed ExplainEntity
  and raw triples; expanded event_type detection
- CLI: invoke_graph_rag, invoke_agent, invoke_document_rag use
  inline entity when available, fall back to graph query
- Tech specs updated

Additional explainability test

trustgraph-base/trustgraph/messaging/translators/agent.py

@@ -1,6 +1,7 @@
 from typing import Dict, Any, Tuple
 from ...schema import AgentRequest, AgentResponse
 from .base import MessageTranslator
+from .primitives import TripleTranslator
 
 
 class AgentRequestTranslator(MessageTranslator):
@@ -49,10 +50,13 @@ class AgentRequestTranslator(MessageTranslator):
 
 class AgentResponseTranslator(MessageTranslator):
     """Translator for AgentResponse schema objects"""
-    
+
+    def __init__(self):
+        self.triple_translator = TripleTranslator()
+
     def decode(self, data: Dict[str, Any]) -> AgentResponse:
         raise NotImplementedError("Response translation to Pulsar not typically needed")
-    
+
     def encode(self, obj: AgentResponse) -> Dict[str, Any]:
         result = {}
 
@@ -75,6 +79,13 @@ class AgentResponseTranslator(MessageTranslator):
         if explain_graph is not None:
             result["explain_graph"] = explain_graph
 
+        # Include explain_triples for explain messages
+        explain_triples = getattr(obj, "explain_triples", [])
+        if explain_triples:
+            result["explain_triples"] = [
+                self.triple_translator.encode(t) for t in explain_triples
+            ]
+
         # Always include error if present
         if hasattr(obj, 'error') and obj.error and obj.error.message:
             result["error"] = {"message": obj.error.message, "code": obj.error.code}

trustgraph-base/trustgraph/messaging/translators/retrieval.py

@@ -1,6 +1,7 @@
 from typing import Dict, Any, Tuple
 from ...schema import DocumentRagQuery, DocumentRagResponse, GraphRagQuery, GraphRagResponse
 from .base import MessageTranslator
+from .primitives import TripleTranslator
 
 
 class DocumentRagRequestTranslator(MessageTranslator):
@@ -28,6 +29,9 @@ class DocumentRagRequestTranslator(MessageTranslator):
 class DocumentRagResponseTranslator(MessageTranslator):
     """Translator for DocumentRagResponse schema objects"""
 
+    def __init__(self):
+        self.triple_translator = TripleTranslator()
+
     def decode(self, data: Dict[str, Any]) -> DocumentRagResponse:
         raise NotImplementedError("Response translation to Pulsar not typically needed")
 
@@ -53,6 +57,13 @@ class DocumentRagResponseTranslator(MessageTranslator):
         if explain_graph is not None:
             result["explain_graph"] = explain_graph
 
+        # Include explain_triples for explain messages
+        explain_triples = getattr(obj, "explain_triples", [])
+        if explain_triples:
+            result["explain_triples"] = [
+                self.triple_translator.encode(t) for t in explain_triples
+            ]
+
         # Include end_of_stream flag (LLM stream complete)
         result["end_of_stream"] = getattr(obj, "end_of_stream", False)
 
@@ -107,6 +118,9 @@ class GraphRagRequestTranslator(MessageTranslator):
 class GraphRagResponseTranslator(MessageTranslator):
     """Translator for GraphRagResponse schema objects"""
 
+    def __init__(self):
+        self.triple_translator = TripleTranslator()
+
     def decode(self, data: Dict[str, Any]) -> GraphRagResponse:
         raise NotImplementedError("Response translation to Pulsar not typically needed")
 
@@ -132,6 +146,13 @@ class GraphRagResponseTranslator(MessageTranslator):
         if explain_graph is not None:
             result["explain_graph"] = explain_graph
 
+        # Include explain_triples for explain messages
+        explain_triples = getattr(obj, "explain_triples", [])
+        if explain_triples:
+            result["explain_triples"] = [
+                self.triple_translator.encode(t) for t in explain_triples
+            ]
+
         # Include end_of_stream flag (LLM stream complete)
         result["end_of_stream"] = getattr(obj, "end_of_stream", False)