The documentation and source code were shared on github.

The issue with blinking and turning off was caused by casting temperature to unsigned... Stupid mistake, fixed. Now it works reliably. To ensure it will work under various heat conditions, I put the whole lamp (except batteries) to a freezer (-18 °C) for 30 minutes, to oven (70 °C) for 30 minutes and repeated 3 times. After such treatment it worked well. Only problem noticed was a bit warped battery box as it got soft in the oven.

To test impact resistance, I dropped the lamp from 2 meters on concrete floor 6 times under various angles (approximation of cube). Unfortunately the lens was a bit too heavy for the LED, when the lamp hit the floor, lens mass pushed on the LED and caused separation of CREE optics from the chip itself. Fix is simple - just use a bit of glue to fix the lens in space.

I guess the project can be marked as finished. All important parts work as expected.