3.8.3: the small picker abstains on chat

The 3.8.0 picker called a tool on 26 percent of sentences that are only chat. Now it leans toward null, drops a pick whose lead is too small, and learned 1,400 more chatty rows: 7 percent on the same sentences.
Tool-level right rate is still 81.2 percent on Turing's nine dev sets; the C matches the Python reference on all 297 golden sentences (QEMU, no network). 26KB of kernel room left.
Part of Turing 10.0; safety bar still short of run 23's 5 percent, so no 10.0 tag. Draft until ci-local is green.

Boot it

The release above includes joshuatree-3.8.3.iso, a bootable disk image. Write it to a USB stick to boot on real hardware:

macOS:

diskutil list                    # find the disk (e.g. disk2)
sudo dd if=joshuatree-3.8.3.iso of=/dev/rdiskN bs=4m

Linux:

lsblk                            # find the device (e.g. sdb)
sudo dd if=joshuatree-3.8.3.iso of=/dev/sdX bs=4M status=progress conv=fsync

This will erase the stick. Double-check the device path first. Boot the machine from the USB stick (F12/F10/Esc/Del at power-on for most PCs) to start the kernel.

The ISO is proven to boot in QEMU (CD-ROM and USB-style raw disk) via the CI regression suite. Real hardware testing is ongoing.