Revert "Move skills watcher to app-server" (#21460)

Reverts openai/codex#21287

codex-rs/mcp-server/src/codex_tool_runner.rs

@@ -362,6 +362,7 @@ async fn run_codex_tool_session_inner(
                     | EventMsg::AgentMessageContentDelta(_)
                     | EventMsg::ReasoningContentDelta(_)
                     | EventMsg::ReasoningRawContentDelta(_)
+                    | EventMsg::SkillsUpdateAvailable
                     | EventMsg::ExitedReviewMode(_)
                     | EventMsg::RequestUserInput(_)
                     | EventMsg::RequestPermissions(_)