Fold per-push Android dev distribution into build-android.yml (which
already builds a signed APK on every master push) instead of a second
workflow that duplicated the whole build. On non-tag master pushes it
stamps a dev versionCode into the working copy of build.gradle and, after
the existing build, ships the play APK to the Play 'internal' track so a
fresh build auto-updates on the phone. Internal testing skips review, so
builds land in minutes; dev builds (code base+1..999) and releases
(base+9000) share the track but stay distinct by versionCode. All new
steps are gated to refs/heads/master (non-tag); the tag/release path is
untouched, and every dev step is continue-on-error so it can never break
the release-critical build.
versionCode = last stable release's code + commits-since-that-tag
(first-parent), staying in the 999-slot band above the release and below
the next version's base. The base is derived from the last stable tag
(not the working tree), so a version bump landing on master before its
tag is pushed can't make dev codes jump ahead and then regress. Logic
lives in tools/android-dev-version-code.js (reusing getAndroidVersionInfo)
with unit tests; it degrades to skip on any anomaly.
Reuses existing keystore/Play/Unsplash secrets; no new secrets.
