Releases were silently no-op'ing on fdroid: versionCode was a hand-maintained
constant, so a commit that didn't bump it rebuilt the same debug_<vc>.apk, the
publish receiver's anti-downgrade guard refused the duplicate (exit 3 =
"nothing to do"), and the CI went green having shipped nothing. build.yml now
patches ProjectConfig's versionCode from `git rev-list --count HEAD` (minus an
offset keeping it continuous with the manual era, last=91) before assembling,
so every main commit auto-produces a new monotonic code. The ProjectConfig
literal is now just the local-dev default.