What should I respond to my ex-supervisor???

After 3 years with this company, I finally had it and I quit. I had a really good relationship with my supervisor, my manager and all of my colleagues at my previous work. I left on good terms and my manager even offered his assistance for anything, if I require it in the future.

The company is really old fashioned and very paper heavy, not with the technology at all which made our work super stressful. Their motto is basically work more with less resources. Everytime, I would bring this up they kept telling me, I just need to manage my time properly and just ask for help. Everyone is struggling with their own work and no one is really available to help me.

I have been a good employee throughout, 6 months in at that job and I got promoted. So, it's only natural that I want to excel further and asked if I can be considered for a more senior role and they turned me down couple of times, they basically said I should just keep doing my job and not think about other position coz I may not be a good fit.

It has been 2 months since I have left that toxic workplace and I have never been happier! Still looking for work but not in any rush. My long time partner is currently supporting me financially so I have time right now to work on myself and improve my mental health. I'm now being cautious on what workplace I want to work with.

Yesterday, my supervisor texted me saying - "Hello there

Heard you are doing well 😉

So are you ready to come back to work yet???"

What do I say to that without being rude? Any suggestion and/or advise would be helpful.

Thanks.