Add resume_agent collab tool (#10903)

Summary
- add the new resume_agent collab tool path through core, protocol, and
the app server API, including the resume events
- update the schema/TypeScript definitions plus docs so resume_agent
appears in generated artifacts and README
- note that resumed agents rehydrate rollout history without overwriting
their base instructions

Testing
- Not run (not requested)

codex-rs/exec/src/event_processor_with_human_output.rs

@@ -796,6 +796,8 @@ impl EventProcessor for EventProcessorWithHumanOutput {
             | EventMsg::UndoStarted(_)
             | EventMsg::ThreadRolledBack(_)
             | EventMsg::RequestUserInput(_)
+            | EventMsg::CollabResumeBegin(_)
+            | EventMsg::CollabResumeEnd(_)
             | EventMsg::DynamicToolCallRequest(_) => {}
         }
         CodexStatus::Running