feat: expose completed-turn message context to memory providers

Adds an optional `messages` keyword to the `MemoryProvider.sync_turn`
contract so external/community memory plugins can receive the OpenAI-style
conversation message list for the completed turn — including assistant tool
calls and tool result content — not just the final assistant text.

Dispatch uses signature inspection (`_provider_sync_accepts_messages`): only
providers that declare a `messages` parameter (or `**kwargs`) receive it; all
existing in-tree providers keep their legacy text-only signature and are
called unchanged. No structured-trace envelope is added to core — providers
reconstruct whatever they need from the standard message list.

Also documents Memori as a standalone community memory provider.

Salvaged from #28065 — rebased onto current main.

Co-authored-by: Dave Heritage <david@memorilabs.ai>

tests/run_agent/test_memory_sync_interrupted.py

@@ -91,6 +91,45 @@ class TestSyncExternalMemoryForTurn:
             session_id="test_session_001",
         )
 
+    def test_completed_turn_syncs_messages_when_present(self):
+        agent = _bare_agent()
+        messages = [
+            {
+                "role": "assistant",
+                "content": None,
+                "tool_calls": [
+                    {
+                        "id": "call-1",
+                        "type": "function",
+                        "function": {
+                            "name": "terminal",
+                            "arguments": "{\"command\":\"pytest\"}",
+                        },
+                    }
+                ],
+            },
+            {
+                "role": "tool",
+                "name": "terminal",
+                "tool_call_id": "call-1",
+                "content": "final Hermes-processed output",
+            }
+        ]
+
+        agent._sync_external_memory_for_turn(
+            original_user_message="run tests",
+            final_response="tests passed",
+            interrupted=False,
+            messages=messages,
+        )
+
+        agent._memory_manager.sync_all.assert_called_once_with(
+            "run tests",
+            "tests passed",
+            session_id="test_session_001",
+            messages=messages,
+        )
+
     # --- Edge cases (pre-existing behaviour preserved) ------------------
 
     def test_no_final_response_skips(self):