Fixing main and make plan mode reasoning effort medium (#9980)

It's overthinking so much on high and going over the context window.

codex-rs/core/src/models_manager/collaboration_mode_presets.rs

@@ -28,7 +28,7 @@ fn plan_preset() -> CollaborationModeMask {
         name: "Plan".to_string(),
         mode: Some(ModeKind::Plan),
         model: None,
-        reasoning_effort: Some(Some(ReasoningEffort::High)),
+        reasoning_effort: Some(Some(ReasoningEffort::Medium)),
         developer_instructions: Some(Some(COLLABORATION_MODE_PLAN.to_string())),
     }
 }