feat(android): add system notification handler

apps/android/app/src/test/java/ai/openclaw/android/node/SystemHandlerTest.kt

@@ -0,0 +1,52 @@
+package ai.openclaw.android.node
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class SystemHandlerTest {
+  @Test
+  fun handleSystemNotify_rejectsUnauthorized() {
+    val handler = SystemHandler.forTesting(poster = FakePoster(authorized = false))
+
+    val result = handler.handleSystemNotify("""{"title":"OpenClaw","body":"hi"}""")
+
+    assertFalse(result.ok)
+    assertEquals("NOT_AUTHORIZED", result.error?.code)
+  }
+
+  @Test
+  fun handleSystemNotify_rejectsEmptyNotification() {
+    val handler = SystemHandler.forTesting(poster = FakePoster(authorized = true))
+
+    val result = handler.handleSystemNotify("""{"title":"   ","body":"  "}""")
+
+    assertFalse(result.ok)
+    assertEquals("INVALID_REQUEST", result.error?.code)
+  }
+
+  @Test
+  fun handleSystemNotify_postsNotification() {
+    val poster = FakePoster(authorized = true)
+    val handler = SystemHandler.forTesting(poster = poster)
+
+    val result = handler.handleSystemNotify("""{"title":"OpenClaw","body":"done","priority":"active"}""")
+
+    assertTrue(result.ok)
+    assertEquals(1, poster.posts)
+  }
+}
+
+private class FakePoster(
+  private val authorized: Boolean,
+) : SystemNotificationPoster {
+  var posts: Int = 0
+    private set
+
+  override fun isAuthorized(): Boolean = authorized
+
+  override fun post(request: SystemNotifyRequest) {
+    posts += 1
+  }
+}