The firstboot script now auto-detects hostname (from hostnamectl) and
MAC address (from first UP interface) at runtime. No URL query parameters
required — just `curl bastion/asahi/firstboot.sh | sudo bash`.
Fixes the shell escaping issue where `&` in query params broke curl piping.
Updated labctl provision asahi instructions accordingly.
Tested on Mac Studio (worker1-k8s0): hostname, MAC, and bastion
registration all auto-detected correctly.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
