gui: fix scrolling to follow content

Use onContentHeightChanged with a re-entry guard to scroll as content
renders. Works for both initial log load and streaming responses.

- followTail tracks user preference (updated on scroll end)
- scrollingNow prevents recursive positionViewAtEnd calls

gui/main.qml

@@ -467,7 +467,6 @@ ApplicationWindow {
                 chatModel.trimFront(20)
             }
         }
-        // Ensure we have the latest session list
         ollie.refreshSessions()
         buildSessionTree()
     }
@@ -476,7 +475,7 @@ ApplicationWindow {
         target: ollie
         function onActiveSessionIdChanged() {
             chatModel.reset()
-            chatView.shouldAutoScroll = true  // Reset scroll state on session switch
+            chatView.followTail = true
             if (ollie.activeSessionId && ollie.activeAgentId) {
                 var log = ollie.readLogForSession(ollie.activeSessionId, ollie.activeAgentId)
                 if (log) {
@@ -487,7 +486,7 @@ ApplicationWindow {
         }
         function onActiveAgentIdChanged() {
             chatModel.reset()
-            chatView.shouldAutoScroll = true  // Reset scroll state on agent switch
+            chatView.followTail = true
             if (ollie.activeSessionId && ollie.activeAgentId) {
                 var log = ollie.readLogForSession(ollie.activeSessionId, ollie.activeAgentId)
                 if (log) {
@@ -883,21 +882,18 @@ ApplicationWindow {
                     boundsBehavior: Flickable.StopAtBounds
                     visible: ollie.daemonConnected && ollie.activeAgentId !== ""
 
-                    // Auto-scroll state: true = follow new content, false = user scrolled up
-                    property bool shouldAutoScroll: true
+                    property bool followTail: true
+                    property bool scrollingNow: false
 
                     onContentHeightChanged: {
-                        // Content grew — scroll to end if we're following
-                        if (shouldAutoScroll && contentHeight > height) {
+                        if (followTail && !scrollingNow && contentHeight > 0) {
+                            scrollingNow = true
                             positionViewAtEnd()
+                            scrollingNow = false
                         }
                     }
 
-                    onMovementEnded: {
-                        // User finished scrolling — update auto-scroll based on position
-                        // atYEnd is true when scrolled to bottom
-                        shouldAutoScroll = atYEnd
-                    }
+                    onMovementEnded: followTail = atYEnd
 
                     delegate: ChatBlockDelegate {
                         width: chatView.width - 8