feat(ui): add header quick-picker for themes and tabs

Palette button left of the cog opens a two-section popup. The themes
section enumerates AllBuiltIns + AllCustom; the tabs section
enumerates Config.Tabs. The active entry gets a leading check-glyph,
inactive rows a same-width blank so labels stay aligned. Click
selects without closing the popup (DontClosePopups).

Theme click triggers the PM-1 crossfade via ThemeRegistry.Switch;
tab click routes through ChangeTab so LastActivityTime stays
consistent with the sidebar and top-bar click paths.

The header input-width reservation now counts the new button plus
the per-button SameLine spacing -- the old formula dropped the
spacing term and overflowed the row once a third button appeared.

HellionChat/Ui/ChatLogWindow.cs

@@ -472,6 +472,107 @@ public sealed class ChatLogWindow : Window
         ChangeTab(newIndex);
     }
 
+    // PM-2b v1.5.4 header quick-picker. Two scrollable sections -- every
+    // built-in plus custom theme, and every tab. Clicking a theme arms
+    // the PM-1 crossfade via ThemeRegistry.Switch; clicking a tab routes
+    // through ChangeTab so LastActivityTime stays consistent with the
+    // sidebar and top-bar click paths. DontClosePopups keeps the popup
+    // open so the user can hop between entries without re-opening it.
+    private void DrawQuickPickerPopup()
+    {
+        using var popup = ImRaii.Popup("##hellion-quick-picker");
+        if (!popup.Success)
+            return;
+
+        ImGui.TextUnformatted(HellionStrings.Settings_QuickPicker_Themes_Header);
+        ImGui.Separator();
+
+        var activeSlug = Plugin.ThemeRegistry.Active.Slug;
+        var allThemes = Plugin
+            .ThemeRegistry.AllBuiltIns()
+            .Concat(Plugin.ThemeRegistry.AllCustom())
+            .ToList();
+
+        using (
+            var scroll = ImRaii.Child(
+                "##hellion-quick-picker-themes",
+                new Vector2(220f, Math.Min(allThemes.Count * 22f, 200f))
+            )
+        )
+        {
+            if (scroll.Success)
+            {
+                foreach (var theme in allThemes)
+                {
+                    var isActive = string.Equals(
+                        theme.Slug,
+                        activeSlug,
+                        StringComparison.OrdinalIgnoreCase
+                    );
+                    DrawQuickPickerGlyph(isActive);
+                    if (
+                        ImGui.Selectable(
+                            $"{theme.Name}##quick-theme-{theme.Slug}",
+                            isActive,
+                            ImGuiSelectableFlags.DontClosePopups
+                        )
+                        && !isActive
+                    )
+                        Plugin.ThemeRegistry.Switch(theme.Slug);
+                }
+            }
+        }
+
+        ImGui.Spacing();
+        ImGui.TextUnformatted(HellionStrings.Settings_QuickPicker_Tabs_Header);
+        ImGui.Separator();
+
+        var tabs = Plugin.Config.Tabs;
+        var activeTabIndex = Plugin.LastTab;
+        using (
+            var scroll = ImRaii.Child(
+                "##hellion-quick-picker-tabs",
+                new Vector2(220f, Math.Min(tabs.Count * 22f, 200f))
+            )
+        )
+        {
+            if (scroll.Success)
+            {
+                for (var i = 0; i < tabs.Count; i++)
+                {
+                    var isActive = i == activeTabIndex;
+                    DrawQuickPickerGlyph(isActive);
+                    if (
+                        ImGui.Selectable(
+                            $"{tabs[i].Name}##quick-tab-{i}",
+                            isActive,
+                            ImGuiSelectableFlags.DontClosePopups
+                        )
+                        && !isActive
+                    )
+                        ChangeTab(i);
+                }
+            }
+        }
+    }
+
+    // Leading check-glyph slot for a quick-picker row. Active rows get a
+    // FontAwesome check; inactive rows get a same-width blank so the
+    // labels stay aligned. The glyph font push stays on its own line so
+    // it never bleeds into the body-font Selectable label.
+    private void DrawQuickPickerGlyph(bool isActive)
+    {
+        using (Plugin.FontManager.FontAwesome.Push())
+        {
+            var check = FontAwesomeIcon.Check.ToIconString();
+            if (isActive)
+                ImGui.TextUnformatted(check);
+            else
+                ImGui.Dummy(new Vector2(ImGui.CalcTextSize(check).X, ImGui.GetTextLineHeight()));
+        }
+        ImGui.SameLine();
+    }
+
     private void TabSwitched(Tab newTab, Tab previousTab)
     {
         // Use the fixed channel if set by the user. Otherwise, if the new tab
@@ -903,7 +1004,15 @@ public sealed class ChatLogWindow : Window
         var buttonWidth = afterIcon.X - beforeIcon.X;
         var showNovice = Plugin.Config.ShowNoviceNetwork && GameFunctions.GameFunctions.IsMentor();
         var buttonsRight = (showNovice ? 1 : 0) + (Plugin.Config.ShowHideButton ? 1 : 0);
-        var inputWidth = ImGui.GetContentRegionAvail().X - buttonWidth * (1 + buttonsRight);
+        // Right-side buttons: quick-picker palette + cog (always present)
+        // plus the optional hide / novice buttons. Each slot costs the
+        // measured button width AND one ItemSpacing for the SameLine gap
+        // in front of it -- leaving the spacing term out overflows the
+        // header row by one gap per button (v1.5.4 quick-picker fix).
+        var rightButtonCount = 2 + buttonsRight;
+        var inputWidth =
+            ImGui.GetContentRegionAvail().X
+            - rightButtonCount * (buttonWidth + ImGui.GetStyle().ItemSpacing.X);
 
         var normalColor = ImGui.GetColorU32(ImGuiCol.Text);
         var push = inputColour != null;
@@ -1013,6 +1122,19 @@ public sealed class ChatLogWindow : Window
 
         ImGui.SameLine();
 
+        if (
+            ImGuiUtil.IconButton(
+                FontAwesomeIcon.Palette,
+                tooltip: HellionStrings.Settings_QuickPicker_Tooltip,
+                width: (int)buttonWidth
+            )
+        )
+            ImGui.OpenPopup("##hellion-quick-picker");
+
+        DrawQuickPickerPopup();
+
+        ImGui.SameLine();
+
         if (ImGuiUtil.IconButton(FontAwesomeIcon.Cog, width: (int)buttonWidth))
             Plugin.SettingsWindow.Toggle();