Cross-platform system tray for `omniroute --tray`: Windows uses a
PowerShell NotifyIcon script (zero native binary, AV-safe); macOS/Linux
use systray2 lazy-installed at runtime into ~/.omniroute/runtime/.
Includes per-platform autostart (LaunchAgent / .desktop / registry) and
`omniroute config tray <enable|disable>` CLI command.
DISPLAY added to env-sync allowlist as an OS/X11 variable, not an
OmniRoute config variable.
