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/tui/src/chatwidget.rs

@@ -4024,6 +4024,8 @@ impl ChatWidget {
             EventMsg::CollabWaitingEnd(ev) => self.on_collab_event(collab::waiting_end(ev)),
             EventMsg::CollabCloseBegin(_) => {}
             EventMsg::CollabCloseEnd(ev) => self.on_collab_event(collab::close_end(ev)),
+            EventMsg::CollabResumeBegin(ev) => self.on_collab_event(collab::resume_begin(ev)),
+            EventMsg::CollabResumeEnd(ev) => self.on_collab_event(collab::resume_end(ev)),
             EventMsg::ThreadRolledBack(_) => {}
             EventMsg::RawResponseItem(_)
             | EventMsg::ItemStarted(_)