fix(android): bound payment transition sampling (#210)

Allow up to two consecutive evidence-free PayActivity transition samples after the single safe Back; fail on the third post-Back sample (200ms cadence) to preserve a finite no-click payment boundary.

android/app/src/main/java/cn/ilapage/goauto/agent/automation/PurchaseLiveAutomation.kt

@@ -117,7 +117,8 @@ class PurchaseLiveAutomation(
             return null
         }
         val labels = linkedSetOf<String>()
-        var backedOutOfPayment = false
+        var paymentBackAttempts = 0
+        var consecutivePaymentSamplesAfterBack = 0
         var backedOutOfChooser = false
         var restoredFromWechat = false
         var pddObservedAfterWechatRestore = false
@@ -170,17 +171,27 @@ class PurchaseLiveAutomation(
             // it permits only bounded reading gestures below, never a payment click.
             val paymentVisible = isKnownPddPaymentActivity(snapshot) && !orderContextVisible && !unpaidContextVisible
             if (paymentVisible) {
-                if (!backedOutOfPayment) {
-                    backedOutOfPayment = true
+                if (paymentBackAttempts == 0) {
+                    paymentBackAttempts++
                     if (!driver.backPurchase()) {
                         return unknown("PURCHASE_ORDER_PAYMENT_BACK_FAILED", "支付页无法安全返回订单详情")
                     }
                     pause(500)
                 } else {
-                    return unknown("PURCHASE_ORDER_PAYMENT_REPEATED", "支付页重复出现，已停止自动核单")
+                    consecutivePaymentSamplesAfterBack++
+                    if (consecutivePaymentSamplesAfterBack >= ORDER_RESULT_PAYMENT_POST_BACK_MAX_SAMPLES) {
+                        return unknown(
+                            "PURCHASE_ORDER_PAYMENT_REPEATED",
+                            "支付页安全返回后持续无订单证据，已停止自动核单" +
+                                "[paymentBackAttempts=$paymentBackAttempts;" +
+                                "consecutivePaymentSamplesAfterBack=$consecutivePaymentSamplesAfterBack]",
+                        )
+                    }
+                    pause(ORDER_RESULT_SAMPLE_INTERVAL_MS)
                 }
                 return@repeat
             }
+            consecutivePaymentSamplesAfterBack = 0
             if (!orderContextVisible && !unpaidContextVisible) {
                 val entries = orderDetailEntryTargets(snapshot)
                 if (entries.size > 1) {
@@ -469,6 +480,7 @@ class PurchaseLiveAutomation(
         const val ORDER_RESULT_MAX_SAMPLES = 60
         const val ORDER_RESULT_MAX_EMPTY_SAMPLES = 15
         const val ORDER_RESULT_WECHAT_RESTORE_MAX_SAMPLES = 15
+        const val ORDER_RESULT_PAYMENT_POST_BACK_MAX_SAMPLES = 3
         const val ORDER_RESULT_SCROLL_SAMPLE_INTERVAL = 15
         const val ORDER_RESULT_SAMPLE_INTERVAL_MS = 200L
     }

android/app/src/test/java/cn/ilapage/goauto/agent/PurchaseLiveAutomationTest.kt

@@ -199,8 +199,25 @@ class PurchaseLiveAutomationTest {
     }
 
     @Test
-    fun `repeated known payment activity still stops without scrolling or payment clicks`() {
-        val driver = LiveDriver(postSubmitCaptureSequence = listOf("payment", "payment"))
+    fun `payment transition frame after safe back reaches unpaid order evidence without payment clicks`() {
+        val driver = LiveDriver(postSubmitCaptureSequence = listOf("payment", "payment", "order"))
+        val automation = PurchaseLiveAutomation(driver, pause = {})
+        val address = automation.updateShippingAddress("_cg55")
+        automation.finalConfirmation(input().copy(addressSuffix = "_cg55"), address)
+        automation.submitOrderOnce()
+
+        val order = automation.readOrderResult()
+
+        assertEquals("PDD-202608210001", order?.orderNo)
+        assertEquals("2026-08-21T02:30:00Z", order?.submittedAt)
+        assertEquals(1, driver.postSubmitBackCount)
+        assertEquals(0, driver.genericSwipes)
+        assertFalse(driver.clicked.any { it.contains("支付") })
+    }
+
+    @Test
+    fun `continuous payment activity still stops at bounded post back samples without payment clicks`() {
+        val driver = LiveDriver(postSubmitCaptureSequence = List(4) { "payment" })
         val automation = PurchaseLiveAutomation(driver, pause = {})
         val address = automation.updateShippingAddress("_cg55")
         automation.finalConfirmation(input().copy(addressSuffix = "_cg55"), address)
@@ -208,6 +225,12 @@ class PurchaseLiveAutomationTest {
 
         assertEquals(null, automation.readOrderResult())
         assertEquals("PURCHASE_ORDER_PAYMENT_REPEATED", automation.lastOrderReadFailure?.code)
+        assertEquals(
+            "支付页安全返回后持续无订单证据，已停止自动核单" +
+                "[paymentBackAttempts=1;consecutivePaymentSamplesAfterBack=3]",
+            automation.lastOrderReadFailure?.message,
+        )
+        assertEquals(4, driver.postSubmitCaptureCount)
         assertEquals(1, driver.postSubmitBackCount)
         assertEquals(0, driver.genericSwipes)
         assertFalse(driver.clicked.any { it.contains("支付") })