feat(ui): lerp sidebar-icon and card-mode-border hover alphas

Sidebar icons ease from 40% to 100% alpha on hover-in via FrameLerp
plus ApplyAlpha. Card-mode borders aggregate row-hover per tab and
lift the border alpha by up to ~+0x70 across every row in that tab.
borderColorAbgr moves into the loop so the per-iteration boost can
apply. ReduceMotion snaps both paths instantly.

Card-hover detection uses IsMouseHoveringRect over the row bounds --
IsItemHovered would only see the 2px spacer dummy below each row.

HellionChat/Ui/ChatLogWindow.cs

@@ -1627,15 +1627,19 @@ public sealed class ChatLogWindow : Window
             var maxLines = Plugin.Config.MaxLinesToRender;
             var startLine = messages.Count > maxLines ? messages.Count - maxLines : 0;
 
-            // Card-mode pre-loop: theme/drawList/winLeft/winRight/border are invariant
+            // Card-mode pre-loop: theme/drawList/winLeft/winRight are
-            // per DrawMessages call; only cursorY moves per row.
+            // invariant per DrawMessages call. borderColorAbgr used to be
+            // hoisted here too, but PM-3d (v1.5.4) modulates it by
+            // tab._cardHoverAlpha per row, so it moves into the AddLine
+            // call below. anyCardHovered aggregates the row-hover state
+            // across all card-rows; the lerp runs once at the loop end so
+            // the next frame paints with the updated alpha.
             var theme = Plugin.ThemeRegistry.Active;
             var drawList = ImGui.GetWindowDrawList();
             var winLeft = ImGui.GetWindowPos().X;
             var winRight = winLeft + ImGui.GetWindowSize().X;
-            var borderColorAbgr = ColourUtil.RgbaToAbgr(
+            var baseBorderRgba = (theme.Colors.Border & 0xFFFFFF00u) | 0x33u;
-                (theme.Colors.Border & 0xFFFFFF00u) | 0x33u
+            var anyCardHovered = false;
-            );
 
             for (var i = startLine; i < messages.Count; i++)
             {
@@ -1791,6 +1795,8 @@ public sealed class ChatLogWindow : Window
                 var useCard = !Plugin.Config.UseCompactDensity;
                 if (useCard)
                 {
+                    var rowStartY = ImGui.GetCursorScreenPos().Y;
+
                     if (message.Sender.Count > 0)
                     {
                         var senderColor =
@@ -1814,9 +1820,18 @@ public sealed class ChatLogWindow : Window
                     else
                         DrawChunks(message.Content, true, handler, lineWidth);
 
-                    // Border bottom as card separator. Alpha reduced to 0x33 for subtlety.
+                    // Border bottom as card separator. Base alpha 0x33;
+                    // PM-3d lifts it by up to ~+0x70 while any row in this
+                    // tab is hovered. _cardHoverAlpha lerps at the loop
+                    // end, so the one-frame lag is invisible at 10f speed.
                     {
                         var rowEndY = ImGui.GetCursorScreenPos().Y;
+                        var hoverBoost = 0.45f * tab._cardHoverAlpha;
+                        var alphaByte = (uint)
+                            Math.Clamp((int)(0x33u + hoverBoost * 255f), 0x33, 0xCC);
+                        var borderColorAbgr = ColourUtil.RgbaToAbgr(
+                            (baseBorderRgba & 0xFFFFFF00u) | alphaByte
+                        );
                         drawList.AddLine(
                             new Vector2(winLeft + 4, rowEndY - 1),
                             new Vector2(winRight - 4, rowEndY - 1),
@@ -1824,6 +1839,17 @@ public sealed class ChatLogWindow : Window
                             1f
                         );
                         ImGui.Dummy(new Vector2(0, 2));
+
+                        // Whole-row hover test. IsItemHovered would only see
+                        // the 2px Dummy above, so hit-test the row rect from
+                        // its start Y down to the separator line instead.
+                        if (
+                            ImGui.IsMouseHoveringRect(
+                                new Vector2(winLeft, rowStartY),
+                                new Vector2(winRight, rowEndY)
+                            )
+                        )
+                            anyCardHovered = true;
                     }
                 }
                 else
@@ -1848,6 +1874,20 @@ public sealed class ChatLogWindow : Window
 
                 message.IsVisible[tab.Identifier] = ImGui.IsItemVisible();
             }
+
+            // PM-3d: update the per-tab card-hover lerp once per
+            // DrawMessages call. ReduceMotion snaps to the target;
+            // otherwise the border alpha eases toward it over a few
+            // frames the next time the rows paint.
+            var cardTarget = anyCardHovered ? 1f : 0f;
+            tab._cardHoverAlpha = Plugin.Config.ReduceMotion
+                ? cardTarget
+                : FrameLerp.Smooth(
+                    tab._cardHoverAlpha,
+                    cardTarget,
+                    speed: 10f,
+                    deltaTime: ImGui.GetIO().DeltaTime
+                );
         }
         catch (ApplicationException)
         {
@@ -2098,7 +2138,19 @@ public sealed class ChatLogWindow : Window
                             ColourUtil.RgbaToAbgr(theme.Colors.Surface)
                         )
                     )
-                    using (ImRaii.PushColor(ImGuiCol.Text, ColourUtil.RgbaToAbgr(iconColor)))
+                    // PM-3c: icon alpha eases from 40% (dim) to 100% on
+                    // hover. _hoverAlpha lerps at the end of this block,
+                    // so the colour for frame N uses frame N-1's value --
+                    // a sub-frame lag that is invisible at 10f speed.
+                    using (
+                        ImRaii.PushColor(
+                            ImGuiCol.Text,
+                            ColourUtil.ApplyAlpha(
+                                ColourUtil.RgbaToAbgr(iconColor),
+                                0.4f + 0.6f * tab._hoverAlpha
+                            )
+                        )
+                    )
                     using (Plugin.FontManager.FontAwesome.Push())
                     {
                         // Button stretches with the configured sidebar width so a
@@ -2110,6 +2162,19 @@ public sealed class ChatLogWindow : Window
                         );
                     }
 
+                    // PM-3c hover-lerp: ramp _hoverAlpha toward 1 while the
+                    // icon button is hovered, back to 0 otherwise.
+                    // ReduceMotion snaps so the dim/full states stay binary.
+                    var hoverTarget = ImGui.IsItemHovered() ? 1f : 0f;
+                    tab._hoverAlpha = Plugin.Config.ReduceMotion
+                        ? hoverTarget
+                        : FrameLerp.Smooth(
+                            tab._hoverAlpha,
+                            hoverTarget,
+                            speed: 10f,
+                            deltaTime: ImGui.GetIO().DeltaTime
+                        );
+
                     if (isCurrentTab)
                     {
                         // Vertical accent pill on the left window edge, 3px wide, half tab height,