android: build.sh installs and syncs the game files when a phone is attached

After building the APK, android/build.sh now picks the attached device (ANDROID_SERIAL for several),
installs the APK (reinstalling on a signature mismatch), syncs the zh client into files/Client and, with
--launch, wakes the phone and starts the app. Without a device it only builds.

push-client.sh is now incremental (android/sync_client.py): the device keeps files/Client/.mt_sync
(size, mtime, path of what the last sync wrote), so later syncs send only new and changed files as one
tar streamed through `adb shell -T run-as` (no copy in /data/local/tmp) and delete the ones gone
locally. Only game resources are synced; settings and logs the app writes there are kept. --locale zh
rebuilds build/zh-locale/Client first when its inputs changed. android/adb_env.sh picks adb and falls
back to server port 5038 when :5037 cannot bind.

Verified against a fake adb device: first sync (1.4 GB, byte-identical), no-op resync, changed files,
deletions, locale switch, --full, the install/launch path and the no-device path.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/adb_env.sh

@@ -0,0 +1,41 @@
+# Sourced by the android/ scripts: picks adb and the target device.
+#   ADB             adb binary (default: $ANDROID_HOME/platform-tools/adb, else adb on PATH)
+#   ANDROID_SERIAL  device to use when several are attached (adb honours it itself)
+# An adb server that cannot bind :5037 ("Address already in use" with nothing listening, seen on this
+# Mac after sleep) is retried on :5038 through ANDROID_ADB_SERVER_PORT.
+SDK="${ANDROID_HOME:-${ANDROID_SDK_ROOT:-$HOME/Library/Android/sdk}}"
+PKG=org.metin2port.client
+if [ -z "${ADB:-}" ]; then
+	if [ -x "$SDK/platform-tools/adb" ]; then ADB="$SDK/platform-tools/adb"; else ADB="$(command -v adb || true)"; fi
+fi
+[ -n "$ADB" ] || { echo "adb not found (install Android platform-tools or set ADB)" >&2; return 1 2>/dev/null || exit 1; }
+if ! "$ADB" start-server >/dev/null 2>&1; then
+	export ANDROID_ADB_SERVER_PORT=5038
+	"$ADB" start-server >/dev/null 2>&1 || { echo "adb server does not start on :5037 or :5038" >&2; return 1 2>/dev/null || exit 1; }
+	echo "adb: :5037 unusable, using :5038"
+fi
+export ADB
+
+# adb_device: sets DEVICE to the one ready device (or ANDROID_SERIAL) and returns 0; returns 1 with a
+# message when none is ready (unauthorized / offline devices are named so the user can fix them).
+adb_device() {
+	local ready others
+	ready=$("$ADB" devices | awk 'NR > 1 && $2 == "device" { print $1 }')
+	others=$("$ADB" devices | awk 'NR > 1 && NF >= 2 && $2 != "device" { print $1 " (" $2 ")" }')
+	if [ -n "${ANDROID_SERIAL:-}" ]; then
+		if printf '%s\n' "$ready" | grep -qxF "$ANDROID_SERIAL"; then DEVICE="$ANDROID_SERIAL"; return 0; fi
+		echo "device $ANDROID_SERIAL is not ready" >&2
+		return 1
+	fi
+	case $(printf '%s' "$ready" | grep -c .) in
+		1) DEVICE="$ready"; export ANDROID_SERIAL="$DEVICE"; return 0 ;;
+		0)
+			if [ -n "$others" ]; then
+				echo "device attached but not ready: $others (unlock the phone and allow USB debugging)" >&2
+			else
+				echo "no Android device attached" >&2
+			fi
+			return 1 ;;
+		*) echo "several devices attached, pick one with ANDROID_SERIAL:" $ready >&2; return 1 ;;
+	esac
+}