fix(android): add screenHash to screen responses, handle goal_failed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android/app/src/main/java/com/thisux/droidclaw/connection/CommandRouter.kt

@@ -4,6 +4,7 @@ import android.util.Base64
 import android.util.Log
 import com.thisux.droidclaw.accessibility.DroidClawAccessibilityService
 import com.thisux.droidclaw.accessibility.GestureExecutor
+import com.thisux.droidclaw.accessibility.ScreenTreeBuilder
 import com.thisux.droidclaw.capture.ScreenCaptureManager
 import com.thisux.droidclaw.model.AgentStep
 import com.thisux.droidclaw.model.GoalStatus
@@ -65,6 +66,10 @@ class CommandRouter(
                 currentGoalStatus.value = if (msg.success == true) GoalStatus.Completed else GoalStatus.Failed
                 Log.i(TAG, "Goal completed: success=${msg.success}, steps=${msg.stepsUsed}")
             }
+            "goal_failed" -> {
+                currentGoalStatus.value = GoalStatus.Failed
+                Log.i(TAG, "Goal failed: ${msg.message}")
+            }
 
             else -> Log.w(TAG, "Unknown message type: ${msg.type}")
         }
@@ -86,9 +91,14 @@ class CommandRouter(
             }
         }
 
+        val screenHash = if (elements.isNotEmpty()) {
+            ScreenTreeBuilder.computeScreenHash(elements)
+        } else null
+
         val response = ScreenResponse(
             requestId = requestId,
             elements = elements,
+            screenHash = screenHash,
             screenshot = screenshot,
             packageName = packageName
         )

android/app/src/main/java/com/thisux/droidclaw/model/Protocol.kt

@@ -23,6 +23,7 @@ data class ScreenResponse(
     val type: String = "screen",
     val requestId: String,
     val elements: List<UIElement>,
+    val screenHash: String? = null,
     val screenshot: String? = null,
     val packageName: String? = null
 )