zstart's venv detection fell back to .venv/Scripts/python.exe (a Windows
binary) whenever it existed. On a Windows-built project accessed from WSL that
file sits on the mount and looks executable, so it got picked and failed with
'exec format error' instead of falling through to python3. Guard that branch to
Windows-family shells (msys/cygwin), where a .exe can actually run.
Verified on WSL: zstart --detached now backgrounds a stdlib app via python3,
serves HTTP 200, logs to /tmp/zstart-<key>.log, and zkill terminates it and
frees the port.
Full port: zhelpers.sh library (jq config, ssh, http/tcp, archive builder,
build-version, motd, port-kill), all commands (zstart/zkill/zrestart/zstop,
zdeploy with 5 kind handlers, zec2/zec2online/zrepair, zbackup/zbackup_ec2/
zsync/zbackup_and_sync, zstart_docker, zsetup_mail, setup_backup_schedule via
cron), Unix-path zconfig.example.json, and a bash/README.md.
Verified: bash -n clean on all scripts; archive exclusions, config semantics,
and zec2 tested against the real config and live server from Git Bash. Needs a
Linux/macOS/WSL shakedown for lsof/rsync/nohup paths before merging.
