Safe safely opened. Here is what I found and learned.
(1) There was a spare magazine in the safe. So, the mostly likely explanation is that when the locksmith flipped the case so that the door was on top, the magazine fell to the bottom of the safe just right so that when the gun fell the trigger fell on to the magazine causing the discharge, which makes sense because the discharge was straight down.
(2) Inspected pistol, no evident defects or unusual wear. Don't believe that it was the pistol's fault.
(3) Pistol had, in fact, re-loaded and re-cocked and was in SA mode ready to fire again. You've heard of "limp wristing"? We now know at a CZ97BD will not jam even when there is "no wristing".
(4) ALL of my firearms will be getting trigger guards or will be holstered, even when in any safe. Even when in my 800lb monster safe. Even when unloaded. That this happened with a de-cocked CZ in DA mode was a tremendous epiphany for me at least.
(5) My $100 high-quality, quick-release safe was opened by this high-inexperienced safe thief in about 8 seconds with a screwdriver. One of the reasons that I purchased a quick-release safe was that if my home was burglarized, and the burglar was still there when I came home, I didn't want him to have access to my pistol and shoot me with it. I can now see that probably anybody who is smart enough to get into my house can probably open a quick-release about as quickly as, well, I can quick-release it.
(6)Thank you Lord that nobody was hurt!