Thanks, but . It took 10 years to fail, so it looks like we may speed up a remodeling project in the master bath, which isn't necessarily a bad thing...just wasn't quite ready to spend the money now.

Unfortunately you can't be sure where the actual leak originates without removing the tile and inspecting. Water follows the path of least resistance and often appears in a place quite different from where the leak occurred. Hopefully you have another shower and are not using this one right now. Get a qualified professional tile contractor in to do the inspection and determine the best approach. A "patch" like you have described is not a likely fix and one that a professional will not perform as the entire shower build is a "system" with approved methods and materials (something your former contractor obviously did not follow). https://www.ceramictilefoundation.org/find-certified-tile-installers

No there is not a full width track as this is a frameless door. They typically just use the small pieces of track as a guide to minimize the amount of metal. Look for a CRL water deflector/wiper seal for shower doors, These get applied with either clear silicone caulk or VHB tape.

I see this pretty often. Very sad as you have spent big $ for a waterproof shower....and this ain't it. I don't know what method was used here, but it obviously didn't work. Sad to say, but the only remedy is to find a reputable tile technician, gut the shower and have it built right. Wish I lived closer to you but I'm in SE Texas.......