agent-orchestrator: add explainability provenance for all patterns (#744)

agent-orchestrator: add explainability provenance for all agent
patterns

Extend the provenance/explainability system to provide
human-readable reasoning traces for the orchestrator's three
agent patterns. Previously only ReAct emitted provenance
(session, iteration, conclusion). Now each pattern records its
cognitive steps as typed RDF entities in the knowledge graph,
using composable mixin types (e.g. Finding + Answer).

New provenance chains:
- Supervisor: Question → Decomposition → Finding ×N → Synthesis
- Plan-then-Execute: Question → Plan → StepResult ×N → Synthesis
- ReAct: Question → Analysis ×N → Conclusion (unchanged)

New RDF types: Decomposition, Finding, Plan, StepResult.
New predicates: tg:subagentGoal, tg:planStep.
Reuses existing Synthesis + Answer mixin for final answers.

Provenance library (trustgraph-base):
- Triple builders, URI generators, vocabulary labels for new types
- Client dataclasses with from_triples() dispatch
- fetch_agent_trace() follows branching provenance chains
- API exports updated

Orchestrator (trustgraph-flow):
- PatternBase emit methods for decomposition, finding, plan, step result, and synthesis
- SupervisorPattern emits decomposition during fan-out
- PlanThenExecutePattern emits plan and step results
- Service emits finding triples on subagent completion
- Synthesis provenance replaces generic final triples

CLI (trustgraph-cli):
- invoke_agent -x displays new entity types inline

trustgraph-base/trustgraph/provenance/namespaces.py

@@ -94,8 +94,14 @@ TG_SYNTHESIS = TG + "Synthesis"
 TG_ANALYSIS = TG + "Analysis"
 TG_CONCLUSION = TG + "Conclusion"
 
+# Orchestrator entity types
+TG_DECOMPOSITION = TG + "Decomposition"  # Supervisor decomposed into sub-goals
+TG_FINDING = TG + "Finding"              # Subagent result
+TG_PLAN_TYPE = TG + "Plan"               # Plan-then-execute plan
+TG_STEP_RESULT = TG + "StepResult"       # Plan step result
+
 # Unifying types for answer and intermediate commentary
-TG_ANSWER_TYPE = TG + "Answer"          # Final answer (Synthesis, Conclusion)
+TG_ANSWER_TYPE = TG + "Answer"          # Final answer (Synthesis, Conclusion, Finding, StepResult)
 TG_REFLECTION_TYPE = TG + "Reflection"  # Intermediate commentary (Thought, Observation)
 TG_THOUGHT_TYPE = TG + "Thought"        # Agent reasoning
 TG_OBSERVATION_TYPE = TG + "Observation" # Agent tool result
@@ -110,6 +116,8 @@ TG_THOUGHT = TG + "thought"        # Links iteration to thought sub-entity
 TG_ACTION = TG + "action"
 TG_ARGUMENTS = TG + "arguments"
 TG_OBSERVATION = TG + "observation" # Links iteration to observation sub-entity
+TG_SUBAGENT_GOAL = TG + "subagentGoal"  # Goal string on Decomposition/Finding
+TG_PLAN_STEP = TG + "planStep"          # Step goal string on Plan/StepResult
 
 # Named graph URIs for RDF datasets
 # These separate different types of data while keeping them in the same collection