feat(ui): add optional regex filter per tab

HellionChat/Ui/SettingsTabs/Tabs.cs

@@ -1,8 +1,10 @@
 using Dalamud.Bindings.ImGui;
 using Dalamud.Game.ClientState.Objects.SubKinds;
 using Dalamud.Interface;
+using Dalamud.Interface.Colors;
 using Dalamud.Interface.Utility.Raii;
 using FFXIVClientStructs.FFXIV.Client.UI;
+using HellionChat._Helpers;
 using HellionChat.Code;
 using HellionChat.Resources;
 using HellionChat.Util;
@@ -238,6 +240,25 @@ internal sealed class Tabs : ISettingsTab
                     }
                 }
             }
+            // UI-8: optional regex filter for this tab.
+            var regexBuffer = tab.MessageRegex ?? string.Empty;
+            if (ImGui.InputText($"{HellionStrings.Settings_Tabs_MessageRegex_Name}##regex-{i}", ref regexBuffer, 256))
+                tab.MessageRegex = string.IsNullOrEmpty(regexBuffer) ? null : regexBuffer;
+            ImGuiUtil.HelpMarker(HellionStrings.Settings_Tabs_MessageRegex_Description);
+
+            // Validity feedback: the settings window is not a hot path, so a
+            // per-frame Compile is fine. An invalid pattern shows a red line and
+            // the tab behaves as if no regex were set.
+            if (!string.IsNullOrEmpty(tab.MessageRegex))
+            {
+                var (_, regexError) = RegexRouteMatcher.Compile(tab.MessageRegex);
+                if (regexError is not null)
+                    ImGui.TextColored(
+                        ImGuiColors.DalamudRed,
+                        string.Format(HellionStrings.Settings_Tabs_MessageRegex_Invalid, regexError)
+                    );
+            }
+
             ImGui.Checkbox(Language.Options_Tabs_PopOut, ref tab.PopOut);
             if (tab.PopOut)
             {