improved android client, feature parity with desktop

scripts/build-android.sh

@@ -7,11 +7,14 @@ android_dir="$repo_root/android"
 
 usage() {
   echo "usage: $0 {debug|check|release|signed|all}"
+  echo
+  echo "  check  ktlint, Android lint and host unit tests — no device needed."
+  echo "         On-device coverage is scripts/android-acceptance.sh."
 }
 
 case "${1:-}" in
   debug) tasks=(assembleDebug) ;;
-  check) tasks=(lintDebug testDebugUnitTest) ;;
+  check) tasks=(ktlintCheck lintDebug testDebugUnitTest) ;;
   release) tasks=(assembleRelease bundleRelease) ;;
   signed)
     required=(
@@ -28,10 +31,42 @@ case "${1:-}" in
     done
     tasks=(assembleRelease bundleRelease)
     ;;
-  all) tasks=(lintDebug testDebugUnitTest assembleDebug assembleRelease bundleRelease) ;;
+  all) tasks=(ktlintCheck lintDebug testDebugUnitTest assembleDebug assembleRelease bundleRelease) ;;
   *) usage >&2; exit 2 ;;
 esac
 
+# The Android toolchain needs JDK 17. A newer JVM does not fail with a version
+# message — the Kotlin compiler throws `IllegalArgumentException: 26.0.2` out of
+# an IntelliJ version parser, which reads as a broken build rather than a wrong
+# JDK. Find 17 before that can happen.
+java_major() {
+  local java_bin="$1"
+  [[ -x "$java_bin" ]] || return 1
+  "$java_bin" -version 2>&1 | sed -n '1s/.*version "\([0-9]*\).*/\1/p'
+}
+
+if [[ "$(java_major "${JAVA_HOME:-}/bin/java" || true)" != "17" ]]; then
+  found=""
+  for candidate in \
+    /usr/lib/jvm/java-17-openjdk \
+    /usr/lib/jvm/java-17-openjdk-amd64 \
+    /usr/lib/jvm/temurin-17-jdk \
+    /Library/Java/JavaVirtualMachines/temurin-17.jdk/Contents/Home; do
+    if [[ "$(java_major "$candidate/bin/java" || true)" == "17" ]]; then
+      found="$candidate"
+      break
+    fi
+  done
+  if [[ -z "$found" ]] && [[ "$(java_major "$(command -v java || echo /nonexistent)" || true)" == "17" ]]; then
+    found="$(dirname "$(dirname "$(readlink -f "$(command -v java)")")")"
+  fi
+  if [[ -z "$found" ]]; then
+    echo "error: JDK 17 is required (see docs/ANDROID.md); set JAVA_HOME to it" >&2
+    exit 1
+  fi
+  export JAVA_HOME="$found"
+fi
+
 if [[ -x "$android_dir/gradlew" ]]; then
   gradle=("$android_dir/gradlew")
 elif command -v gradle >/dev/null 2>&1; then