feat(chat): add pin message contract scaffolding

apps/flipcash/shared/chat/src/main/kotlin/com/flipcash/shared/chat/internal/delegates/EventStreamDelegate.kt

@@ -458,6 +458,11 @@ class EventStreamDelegate @Inject constructor(
                     // replacement rules, so they overwrite the cached ones.
                     metadataDataSource.updateRules(chatId, metaUpdate.newRules)
                 }
+                is MetadataUpdate.PinsChanged -> {
+                    // Convergent like the roster: applied only when strictly newer than the held
+                    // summary, so a replayed or reordered event cannot roll the pins back.
+                    metadataDataSource.updatePinSummary(chatId, metaUpdate.summary)
+                }
             }
         }
 

apps/flipcash/shared/chat/src/test/kotlin/com/flipcash/shared/chat/PinsChangedStreamTest.kt

@@ -0,0 +1,65 @@
+package com.flipcash.shared.chat
+
+import com.flipcash.app.persistence.sources.ChatMetadataDataSource
+import com.flipcash.services.controllers.EventStreamingController
+import com.flipcash.services.models.chat.ChatId
+import com.flipcash.services.models.chat.ChatUpdate
+import com.flipcash.services.models.chat.MetadataUpdate
+import com.flipcash.services.models.chat.PinChange
+import com.flipcash.services.models.chat.PinSummary
+import com.flipcash.shared.chat.internal.ChatStateHolder
+import com.flipcash.shared.chat.internal.delegates.EventStreamDelegate
+import io.mockk.every
+import io.mockk.mockk
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.flow.flowOf
+import org.junit.Test
+
+/**
+ * A `PinsChanged` event hands its summary to the data source, which applies it only when strictly
+ * newer than the held one (see `ChatMetadataDaoTest` for that rule).
+ */
+class PinsChangedStreamTest {
+
+    @Test
+    fun `a pins changed event offers its summary to the held pins`() {
+        val chatId = ChatId("aabbccdd")
+        val summary = PinSummary(count = 1, version = 7)
+        val update = ChatUpdate(
+            chatId = chatId,
+            metadataUpdates = listOf(
+                MetadataUpdate.PinsChanged(change = PinChange.Unpinned(messageId = 9), summary = summary),
+            ),
+        )
+        val streaming = mockk<EventStreamingController>(relaxed = true)
+        every { streaming.isConnected } returns true
+        every { streaming.chatUpdates } returns flowOf(update)
+        val metadata = mockk<ChatMetadataDataSource>(relaxed = true)
+        val scope = CoroutineScope(SupervisorJob() + Dispatchers.Unconfined)
+
+        try {
+            EventStreamDelegate(
+                eventStreamingController = streaming,
+                messagingController = mockk(relaxed = true),
+                metadataDataSource = metadata,
+                messageDataSource = mockk(relaxed = true),
+                memberDataSource = mockk(relaxed = true),
+                tokenCoordinator = mockk(relaxed = true),
+                userManager = mockk(relaxed = true),
+                stateHolder = ChatStateHolder(),
+                analytics = mockk(relaxed = true),
+                exchange = mockk(relaxed = true),
+            ).apply {
+                initialize(scope)
+                open()
+            }
+
+            io.mockk.coVerify(timeout = 5_000) { metadata.updatePinSummary(chatId, summary) }
+        } finally {
+            scope.cancel()
+        }
+    }
+}