gplay release flow

Drive the Google Play release lifecycle with gplay releases: upload a build to a track, promote it up the ladder, run a staged rollout on production (halt / resume / complete it), and list what a track holds.

Shared conventions are in gplay-cli-usage; onboarding auth is gplay-setup.

Mental model: the track ladder + the rollout state machine

A build is uploaded to one track (internal, alpha, beta, production, or any custom closed-track name) and then promoted up the ladder: the same versionCode, no AAB re-upload. On a track, the latest release moves through a small state machine: