A version that should actually work for people besides me
Major bug fixed in 49b1705: authentication/setup sequence was totally wrong, which made it somewhere between unreliable and non-functional. I must've been sleep-deprived when I extracted these from the logs, and somehow it worked with my own TomTom Runner (though no one else's, it seems).
After cleaning this up, I can now confirm that ttblue works for a brand new device after factory reset 👍.
I also made it so ttblue intelligently chooses the correct maximum packet rate for writing files to the watch in d9a1513. (Currently, it only writes the time offset settings, and the QuickFixGPS update, but it could write others too.)