gplay customapps (managed Google Play private apps)

One experimental command, customapps create. It creates a Custom app, a private Android app distributed to one organisation through managed Google Play. This is the only Play Developer API path that creates an app record (public apps can only be created in the Play Console). Shared conventions (auth, output, exit codes, --dry-run/--confirm) are in gplay-cli-usage.

Create a custom app

# Rehearse first, validates inputs + artifact, no HTTP, reports the gate:
gplay customapps create ./app-release.aab \
  --title "Acme Internal" --default-language en-US --dry-run

# Live (irreversible), requires --confirm:
gplay customapps create ./app-release.aab \
  --title "Acme Internal" --default-language en-US --confirm