flash-mac.sh: macOS DiskArbitration re-probes the stick the moment the zap lands and can hold it while sgdisk writes the primary header, leaving a torn table (backup OK, primary ERROR) that only surfaced as "partition did not appear". sgdisk output is now visible, the table is verified after writing and retried up to three times. The wifi preset log line counts the list instead of saying 6. ac-os pull: one transient HEAD failure on the CDN skipped the universal-files block and flashed the cached copies, a new kernel over the previous release's initramfs with no kpart, silently. HEAD checks now retry five times and a still-unreachable CDN refuses to flash; only a genuine 404 (a release without those files) falls through to the legacy path. Same for the Chromebook kpart, which would otherwise silently drop KERN-A.