Export ANDROID_SERIAL for precise device selection

This ensures that the `ANDROID_SERIAL` environment variable is exported
when
`ADB_SERIAL` is set. This is crucial because Android Gradle Plugin's
`android.injected.device.serial` property can silently fall back to
selecting
all attached devices if the serial doesn't match exactly. Exporting
`ANDROID_SERIAL` provides a deeper level of filtering for spawned `adb`
binaries, maintaining the intended device selection.

watch/wearos/run.sh

@@ -308,6 +308,12 @@ apply_target() {
     fi
     if [[ -n "$ADB_SERIAL" ]]; then
         GRADLE_PROPS+=("-Pandroid.injected.device.serial=$ADB_SERIAL")
+        # AGP's `android.injected.device.serial` silently falls back to "all
+        # attached devices" when the serial doesn't match exactly (notably
+        # with mDNS-TLS serials like adb-<hwid>-<suffix>._adb-tls-connect._tcp).
+        # ANDROID_SERIAL works one level deeper on every spawned adb binary,
+        # so the filter holds even when AGP's own matcher doesn't.
+        export ANDROID_SERIAL="$ADB_SERIAL"
     fi
 }