Confirmation of the fix.

• I let the toaster oven sit for a day, in case there was any residual internal water I missed, then used it as a toaster - at least that showed my work didn't make it worse.

• I filled the big transparent tank with water and put it on the toaster oven.

• I emptied the tank and put it back on the toaster oven. So now there was just what residual water remained.

• I set the toaster oven for "Bread", 400°, 30 minutes. I started it with no bread, just as a test. It started its regular cycle, producing the expected steam for the first 10 minutes, just running off the residual water.

• I let the toaster oven cool down, and ran it again. This time, I got the "Add water" indicator after a few minutes, so I just cancelled the rest of the run. This proves that enough water flows through the system to run the steam function, and the "Add water" detector still works.