Some good advice above. Especially from sobelri. When he asked about the pot, I was afraid that you were going to say that the tree was in a black plastic pot. A combination of a black plastic nursery pot and full Houston summer sun is almost sure death for a fruit tree. Unless you can keep it watered about twice a day to keep it cooled down. I paint all my plastic nursery pots white, or keep the pots shaded.
I think your main original problem is that your tree got way to hot and dry with that pot in our summer sun, and the roots seriously overheated and most died.
I moved almost all my potted trees, even the ones in white SIP containers, to more shaded areas week ago. Leaving them morning and some noonday sun, but shade in afternoon.
Just keep your tree in the shade and well watered for as long as it takes to recover. Maybe the rest of the year. The shade will not hurt it, and may save the tree.
If you lose the tree just remember the Houston Garden Center will start their 70% off sale in the next week or two, and you should be able to get a health Celeste for about $10. But hopefully your's will recover. Best of luck!
You can also PM me if you want, as I have a few Celeste that I have rooted recently as 'give away trees" for people who ask about my figs. I am trying to keep a few on hand all the time for this.
CliffH