CLI App Test Notification

`ed app test-notification`

Sends the same test notification the settings pane sends.

ed app test-notification [--json]

Name	Type / values	Default	What it does
`--json`	flag	off	Emit JSON on stdout.

--json shape:

{
  "action": "test-notification",
  "requested": true
}

Examples:

ed app test-notification
ed app test-notification --json

Without --json it prints test-notification requested. It needs the menu bar helper and exits 4 otherwise. The notification is sent by the Agent Usage notifier, so it needs the usage extension on as well as the helper running; with that extension off, nothing is sent and ed still exits 0. The helper discards the notifier's own answer, so a notification blocked in System Settings is silent here too: ed permissions request notifications is the fix.