[FEATURE] make it obvious when you've been throttled to Sonnet

I've noticed that sometimes in a long working session with Opus ($200 max sub) Claude Code will revert to Sonnet once I've used up all my credits. However, often I don't notice this because it's in the middle of many changes that Claude Code is making, and the notification gets lost in the long thread of edits.

This is actually REALLY annoying, because the quality plummets without me realizing, and it takes me often an hour or more to realize, "Hang on a second, why is this thing suddenly making more mistakes... wait, is this SONNET??!".

I think the Claude Code team probably doesn't realize how annoying this is because they don't have limits on their Opus usage. A simple fix would be to just display the model name (Sonnet in this case) in the status bar once you've been throttled, so it doesn't take hours to figure it out.