Set the version once, in one place, for every artefact

The workspace read 0.1.0 for two releases, so every desktop binary reported a
version two releases stale. The APK was worse: `AndroidManifest.xml` states no
version at all, so a device showed `versionName=null` and `versionCode=0` while
the library inside the APK knew exactly what it was. A version edited by hand
in several files is a version that is wrong in at least one of them.

`tools/set-version.sh` is now the only thing that sets one. It takes the
version from the latest git tag, or is told, and writes the two files that must
state it before anything is built: the workspace `Cargo.toml`, from which every
crate inherits, and `packaging/PKGBUILD`, which pacman reads before a build
exists. It refreshes `Cargo.lock`, because members appear there by version and
CI builds `--locked`. `--commit` commits the result.

Android is not in that list on purpose. `package.sh` reads the version out of
`Cargo.toml` and hands it to `aapt2 link`, so the APK cannot drift from the
binary it contains — there is no third file to forget. `versionCode` has to be
one increasing integer, which a semantic version is not, so it is packed as
MAJOR*10000 + MINOR*100 + PATCH: ordered the way Android requires, and readable
at a glance.

A version that is not MAJOR.MINOR.PATCH is refused rather than coerced. It is
a contract with whoever reads a bug report, and silently turning "0.4" into
something else is worse than being asked to type it again.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docker/android/package.sh

@@ -27,6 +27,26 @@ CACHE="${XDG_CACHE_HOME:-${HOME}/.cache}/darkroom-android"
 OUT="${CACHE}/target/apk"
 APK="${OUT}/darkroom.apk"
 
+# The version, taken from the workspace rather than restated here.
+#
+# `AndroidManifest.xml` deliberately declares none: a manifest that states a
+# version is a second place for one to be wrong, and it was — the APK reported
+# `versionName=null` and `versionCode=0` on the device while the binary inside
+# it knew perfectly well what it was.
+#
+# `versionCode` must be a single increasing integer, which a semantic version
+# is not, so it is packed: MAJOR*10000 + MINOR*100 + PATCH. That keeps the
+# ordering Android needs (it refuses to install an APK whose code is lower than
+# the installed one) and stays readable — 0.4.0 is 400. It allows 99 minors and
+# 99 patches per major, which is a limit worth knowing about and a long way off.
+VERSION_NAME="$(sed -n 's/^version = "\(.*\)"$/\1/p' "${REPO}/Cargo.toml" | head -1)"
+if [[ -z "${VERSION_NAME}" ]]; then
+    echo "error: no version in Cargo.toml" >&2
+    exit 1
+fi
+VERSION_CODE="$(awk -F. '{ print $1 * 10000 + $2 * 100 + $3 }' <<< "${VERSION_NAME}")"
+echo "==> version ${VERSION_NAME} (code ${VERSION_CODE})"
+
 INSTALL=0
 [[ "${1:-}" == "--install" ]] && INSTALL=1
 
@@ -100,6 +120,8 @@ echo "==> packaging APK"
         -R "${OUT}/res.zip" \
         --min-sdk-version 28 \
         --target-sdk-version 36 \
+        --version-name "'"${VERSION_NAME}"'" \
+        --version-code "'"${VERSION_CODE}"'" \
         -o "${OUT}/base.apk" \
         --auto-add-overlay