feat(memory): add audit export surface

docs/memory-graph-runtime.md

@@ -21,10 +21,10 @@ with `markitect-tool`.
 - `InMemoryMemoryGraphRepository` provides deterministic local storage for
   tests and future service wiring.
 - `MemoryRuntimeService.import_markitect_graph()` persists an imported graph and
-  can attach an audit event when an `OperationContext` is supplied.
+  persists an audit event when an `OperationContext` is supplied.
 - `MemoryRuntimeService.query_memory()` retrieves graph nodes through a scope
   policy check plus per-node policy checks, returns source-grounded context
-  items, preserves safe denied diagnostics, and emits an audit event in the
+  items, preserves safe denied diagnostics, and persists an audit event in the
   result envelope.
 - `MemoryRuntimeService.apply_retention()` marks stale memories for review or
   transitions old memories to `delete_requested` without physical deletion.
@@ -40,6 +40,12 @@ with `markitect-tool`.
 - `MemoryRuntimeService.export_context_package_inputs()` emits
   Markitect-compatible context package input envelopes without invoking the
   Markitect compiler.
+- `MemoryGraphRepository` persists memory audit events separately from
+  Markitect memory events, allowing operations to be queried by graph,
+  correlation id, and operation.
+- `MemoryRuntimeService.export_runtime_envelope()` emits a portable runtime
+  envelope containing graph nodes, edges, memory events, and audit traces with
+  operation id, actor, policy decision, and filter metadata.
 
 ## Boundary
 
@@ -53,6 +59,7 @@ with `markitect-tool`.
 
 - runtime ids and persistence
 - append-only event storage
+- durable audit event storage
 - permission-aware retrieval and context assembly
 - retention, refresh, compaction, review gates, and audit behavior
 - agent-safe update plans and Markitect-compatible export envelopes