chore: morpheus to path (#18353)

Make the morpheus agent (which is the phase 2 memories agent) follow the
agent-v2 path system by naming it `/morpheus`. To maintain the path
primitive this means moving it to a dedicated `AgentControl`

Co-authored-by: Codex <noreply@openai.com>

codex-rs/protocol/src/protocol.rs

@@ -2723,6 +2723,9 @@ impl SessionSource {
             SessionSource::SubAgent(SubAgentSource::ThreadSpawn { agent_path, .. }) => {
                 agent_path.clone()
             }
+            SessionSource::SubAgent(SubAgentSource::MemoryConsolidation) => {
+                Some(AgentPath::morpheus())
+            }
             _ => None,
         }
     }