Fix incorrect property names in explainability (#698)

Remove type suffixes from explainability dataclass fields + fix show_explain_trace

Rename dataclass fields to match KG property naming conventions:
- Analysis: thought_uri/observation_uri → thought/observation
- Synthesis/Conclusion/Reflection: document_uri → document

Fix show_explain_trace for current API:
- Resolve document content via librarian fetch instead of removed
  inline content fields (synthesis.content, conclusion.answer)
- Add Grounding display for DocRAG traces
- Update fetch_docrag_trace chain: Question → Grounding → Exploration →
Synthesis
- Pass api/explain_client to all print functions for content resolution

Update all CLI tools and tests for renamed fields.

trustgraph-cli/trustgraph/cli/invoke_graph_rag.py

@@ -728,8 +728,8 @@ def _question_explainable_api(
 
                 elif isinstance(entity, Synthesis):
                     print(f"\n  [synthesis] {prov_id}", file=sys.stderr)
-                    if entity.document_uri:
-                        print(f"    Document: {entity.document_uri}", file=sys.stderr)
+                    if entity.document:
+                        print(f"    Document: {entity.document}", file=sys.stderr)
 
                 else:
                     if debug: