fix(ui): render scroll-to-bottom button as a parent overlay

The button was drawn inside the ##chat2-messages child via SetCursorPos,
which inflated ContentSize.y / ScrollMaxY each frame (causing positional
drift) and was clipped by the scrollbar's inner clip rect (causing right-
edge cutoff). Move it to the parent window using screen-space coordinates
captured before the child opens; the scroll state is cached inside the
child while GetScrollMaxY/Y still refer to the child's scroll context.

HellionChat/Ui/ChatLogWindow.cs

@@ -780,6 +780,10 @@ public sealed class ChatLogWindow : Window
     // frame's scroll-snap check forces a jump to the live end.
     private bool _scrollToBottomRequested;
 
+    // UI-5: cached each frame inside the ##chat2-messages child. True when the
+    // user has scrolled up enough that the overlay button should be shown.
+    private bool _childScrolledUp;
+
     public override void Draw()
     {
         DrewThisFrame = true;
@@ -1547,14 +1551,37 @@ public sealed class ChatLogWindow : Window
         bool switchedTab
     )
     {
-        using var child = ImRaii.Child("##chat2-messages", new Vector2(-1, childHeight));
-        if (!child.Success)
-            return;
+        // Capture these before entering the child so we can position the overlay
+        // button in the parent window's coordinate space afterward. Inside the
+        // child the same queries would return child-local values.
+        var childScreenPos = ImGui.GetCursorScreenPos();
+        var childWidth     = ImGui.GetContentRegionAvail().X;
 
-        if (tab.DisplayTimestamp && Plugin.Config.PrettierTimestamps)
-            DrawLogTableStyle(tab, handler, switchedTab);
-        else
-            DrawLogNormalStyle(tab, handler, switchedTab);
+        using (var child = ImRaii.Child("##chat2-messages", new Vector2(-1, childHeight)))
+        {
+            if (child.Success)
+            {
+                if (tab.DisplayTimestamp && Plugin.Config.PrettierTimestamps)
+                    DrawLogTableStyle(tab, handler, switchedTab);
+                else
+                    DrawLogNormalStyle(tab, handler, switchedTab);
+
+                // Cache scroll state while we are still inside the child so
+                // GetScrollMaxY / GetScrollY refer to the child's scroll context.
+                _childScrolledUp = ImGui.GetScrollMaxY() - ImGui.GetScrollY() > 1f;
+            }
+            else
+            {
+                _childScrolledUp = false;
+            }
+        }
+
+        // Draw the overlay button in the parent window, outside the child.
+        // This prevents the button from inflating ScrollMaxY inside the child
+        // (which caused it to drift) and avoids the scrollbar's inner clip rect
+        // (which caused it to be cut off on the right edge).
+        if (_childScrolledUp)
+            DrawScrollToBottomButtonOverlay(childScreenPos, childWidth, childHeight);
     }
 
     private void DrawLogNormalStyle(Tab tab, PayloadHandler handler, bool switchedTab)
@@ -1567,8 +1594,6 @@ public sealed class ChatLogWindow : Window
         _scrollToBottomRequested = false;
 
         handler.Draw();
-
-        DrawScrollToBottomButton();
     }
 
     private void DrawLogTableStyle(Tab tab, PayloadHandler handler, bool switchedTab)
@@ -1604,27 +1629,30 @@ public sealed class ChatLogWindow : Window
             }
         }
 
-        // Draw the scroll-to-bottom button after EndTable so it renders as a
-        // post-table overlay, not inside an active table cell. The outer
-        // ItemSpacing=Zero push has ended; restore normal spacing so the button
-        // position matches the DrawLogNormalStyle path.
-        using (ImRaii.PushStyle(ImGuiStyleVar.ItemSpacing, oldItemSpacing))
-            DrawScrollToBottomButton();
     }
 
-    // UI-5: floating jump-to-latest button, shown only while the user has
-    // scrolled up from the live end. Pinned to the bottom-right of the visible
-    // viewport inside the scrolling child (cursor coords are content-space, the
-    // viewport is [ScrollY, ScrollY + WindowHeight]).
-    private void DrawScrollToBottomButton()
+    // UI-5: floating jump-to-latest button, drawn in the PARENT window after the
+    // ##chat2-messages child closes. Placing it here prevents two bugs:
+    // 1. Inside the child, SetCursorPos adds to CursorMaxPos.y and inflates
+    //    ContentSize.y / ScrollMaxY every frame, so the button chased its own
+    //    shadow and never landed at a stable position.
+    // 2. GetWindowWidth() inside the child includes the scrollbar column, so the
+    //    button overlapped the scrollbar and was clipped by the inner clip rect.
+    // Screen-space positioning via SetCursorScreenPos is immune to both.
+    private void DrawScrollToBottomButtonOverlay(
+        Vector2 childScreenPos,
+        float childWidth,
+        float childHeight)
     {
-        if (ImGui.GetScrollMaxY() - ImGui.GetScrollY() <= 1f)
-            return;
+        var size           = ImGui.GetFrameHeight();
+        var pad            = 8f * ImGuiHelpers.GlobalScale;
+        var scrollbarWidth = ImGui.GetStyle().ScrollbarSize;
 
-        var size = ImGui.GetFrameHeight();
-        var pad = 8f * ImGuiHelpers.GlobalScale;
-        ImGui.SetCursorPosX(ImGui.GetScrollX() + ImGui.GetWindowWidth() - size - pad);
-        ImGui.SetCursorPosY(ImGui.GetScrollY() + ImGui.GetWindowHeight() - size - pad);
+        var btnPos = new Vector2(
+            childScreenPos.X + childWidth  - scrollbarWidth - size - pad,
+            childScreenPos.Y + childHeight -                  size - pad);
+
+        ImGui.SetCursorScreenPos(btnPos);
 
         if (ImGuiUtil.IconButton(
                 FontAwesomeIcon.ArrowDown,