ls glob on empty cache dir exits non-zero and kills script under
set -euo pipefail. Switched to find which exits 0 on no matches.
Same fix for grep|sed pipeline in device selection; added empty
DEVICE guard.
Single script covers full drop implant prep: image download and flash,
WiFi (with UUID fix), per-device SSH keygen to Infisical, mode selection,
VPN (Tailscale/WireGuard), network alerter webhook, and first-boot service.
Insert card, power on, walk away.
Cobra