feat(ui): add scroll-to-bottom button to the chat log

HellionChat/Ui/ChatLogWindow.cs

@@ -776,6 +776,10 @@ public sealed class ChatLogWindow : Window
     // (~17ms at 60fps) late, invisible inside the post-reload Atlas-Build.
     private bool _firstFrameDone;
 
+    // UI-5: set when the user clicks the scroll-to-bottom button; the next
+    // frame's scroll-snap check forces a jump to the live end.
+    private bool _scrollToBottomRequested;
+
     public override void Draw()
     {
         DrewThisFrame = true;
@@ -1558,10 +1562,13 @@ public sealed class ChatLogWindow : Window
         using (ImRaii.PushStyle(ImGuiStyleVar.ItemSpacing, Vector2.Zero))
             DrawMessages(tab, handler, false);
 
-        if (switchedTab || ImGui.GetScrollY() >= ImGui.GetScrollMaxY())
+        if (switchedTab || _scrollToBottomRequested || ImGui.GetScrollY() >= ImGui.GetScrollMaxY())
             ImGui.SetScrollHereY(1f);
+        _scrollToBottomRequested = false;
 
         handler.Draw();
+
+        DrawScrollToBottomButton();
     }
 
     private void DrawLogTableStyle(Tab tab, PayloadHandler handler, bool switchedTab)
@@ -1588,12 +1595,41 @@ public sealed class ChatLogWindow : Window
                 // Custom styles can have cellPadding that go above 4, which GetScrollY isn't respecting
                 var cellPaddingOffset =
                     !compact && oldCellPadding.Y > 4f ? oldCellPadding.Y - 4f : 0f;
-                if (switchedTab || ImGui.GetScrollY() + cellPaddingOffset >= ImGui.GetScrollMaxY())
+                if (switchedTab || _scrollToBottomRequested
+                    || ImGui.GetScrollY() + cellPaddingOffset >= ImGui.GetScrollMaxY())
                     ImGui.SetScrollHereY(1f);
+                _scrollToBottomRequested = false;
 
                 handler.Draw();
             }
         }
+
+        // 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()
+    {
+        if (ImGui.GetScrollMaxY() - ImGui.GetScrollY() <= 1f)
+            return;
+
+        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);
+
+        if (ImGuiUtil.IconButton(
+                FontAwesomeIcon.ArrowDown,
+                tooltip: HellionStrings.ChatLog_ScrollToBottom_Tooltip))
+            _scrollToBottomRequested = true;
     }
 
     private void DrawMessages(