[exec] Enable update_plan tool

Author: dylan-hurd-oai

codex-rs/exec/src/lib.rs

@@ -146,7 +146,7 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
         model_provider,
         codex_linux_sandbox_exe,
         base_instructions: None,
-        include_plan_tool: None,
+        include_plan_tool: Some(true),
         include_apply_patch_tool: None,
         include_view_image_tool: None,
         show_raw_agent_reasoning: oss.then_some(true),