fix(chat): serialize scroll follow and timeline jumps (#1322, #1323) (#1359)

app/src/androidTest/java/com/m57/hermescontrol/ui/chat/fullbleed/FullBleedChatListTest.kt

@@ -3,6 +3,8 @@ package com.m57.hermescontrol.ui.chat.fullbleed
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyListState
+import androidx.compose.runtime.SideEffect
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.test.assertCountEquals
@@ -12,6 +14,9 @@ import androidx.compose.ui.test.junit4.createComposeRule
 import androidx.compose.ui.test.onAllNodesWithTag
 import androidx.compose.ui.test.onNodeWithTag
 import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.onRoot
+import androidx.compose.ui.test.performTouchInput
+import androidx.compose.ui.test.swipeDown
 import androidx.compose.ui.unit.dp
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.filters.MediumTest
@@ -25,6 +30,7 @@ import com.m57.hermescontrol.ui.chat.ToolStatus
 import com.m57.hermescontrol.ui.chat.components.ChatScrollController
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import org.junit.Assert.assertFalse
 import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -72,9 +78,18 @@ class FullBleedChatListTest {
         showUserMessageTokens: Boolean = true,
         showAssistantMessageTokens: Boolean = true,
         showTokensPerSecond: Boolean = true,
+        onController: (ChatScrollController) -> Unit = {},
     ) {
         composeTestRule.setContent {
-            val listState = LazyListState()
+            val listState = remember { LazyListState() }
+            val scrollController =
+                remember(listState) {
+                    ChatScrollController(
+                        listState = listState,
+                        scope = CoroutineScope(Dispatchers.Main.immediate),
+                    )
+                }
+            SideEffect { onController(scrollController) }
             FullBleedChatList(
                 transcript =
                     TranscriptUiState.resolve(
@@ -106,15 +121,24 @@ class FullBleedChatListTest {
                 actions = testTranscriptActions(),
                 searchState = ChatSearchState(),
                 listState = listState,
-                scrollController =
-                    ChatScrollController(
-                        listState = listState,
-                        scope = CoroutineScope(Dispatchers.Main.immediate),
-                    ),
+                scrollController = scrollController,
             )
         }
     }
 
+    @Test
+    fun upwardUserGesture_pausesBottomFollow() {
+        lateinit var scrollController: ChatScrollController
+        render(
+            messages = List(40) { index -> msg("u$index", MessageRole.USER) },
+            onController = { scrollController = it },
+        )
+        composeTestRule.runOnIdle { scrollController.jumpToBottom() }
+        composeTestRule.waitForIdle()
+        composeTestRule.onRoot().performTouchInput { swipeDown() }
+        composeTestRule.runOnIdle { assertFalse(scrollController.isFollowingBottom) }
+    }
+
     @Test
     fun userMessages_keepBubble_agentProse_isFullBleed() {
         render(