Our 5-year-old refuses to nap but crashes hard by 4 PM — how to keep energy up without meltdown?

Lately, our 5-year-old has completely dropped their afternoon nap, which I guess is normal at this age, but it’s been throwing off the whole day. By around 4 PM, they’re totally wiped out and start getting super cranky and irritable, which makes the evening routine a battle. We’ve tried quiet time with books or puzzles instead of napping, but it only delays the inevitable meltdown. The tricky part is that I work from home, so I can’t just put them down for a nap whenever - they need to be somewhat independent during my calls. I’d love to find a way to keep their energy more stable so we can have a smoother late afternoon and evening. We’ve tried adjusting breakfast and lunch to include more protein and snacks, but it doesn’t seem to help much. Has anyone dealt with a similar no-nap, early crash situation? What kind of activities or snacks helped keep your kiddo energized and happy through the afternoon without a meltdown? And how did you manage your own work schedule around it?