feat(ui): add SymbolPicker popup with FFXIV icon tab

New popup attached to the chat input lets the user browse and insert
Dalamud SeIconChar glyphs (161 PUA codepoints, server-safe by design).
Search field filters by enum name. Multi-insert keeps the popup open
until the user clicks elsewhere. BMP tab follows in the next commit.

HellionChat/Ui/ChatLogWindow.cs

@@ -40,6 +40,7 @@ public sealed class ChatLogWindow : Window
 
     private readonly CommandWrapper _clearHellionCommand;
     private readonly CommandWrapper _hellionCommand;
+    private readonly SymbolPicker _symbolPicker;
 
     internal bool ScreenshotMode;
     private string Salt { get; }
@@ -129,6 +130,8 @@ public sealed class ChatLogWindow : Window
         _clearHellionCommand.Execute += ClearLog;
         _hellionCommand.Execute += ToggleChat;
 
+        _symbolPicker = new SymbolPicker();
+
         Plugin.ClientState.Login += Login;
         Plugin.ClientState.Logout += Logout;
 
@@ -792,6 +795,30 @@ public sealed class ChatLogWindow : Window
         )
             inputColour = ecColour;
 
+        // Symbol-picker trigger sits left of the channel indicator. ImRaii.Popup
+        // inside DrawAndConsume pins to the last rendered item, so the call MUST
+        // run immediately after this IconButton — placing it after the channel
+        // picker below would pin the popup under the wrong widget.
+        if (ImGuiUtil.IconButton(
+                FontAwesomeIcon.Smile,
+                "symbol-picker-trigger",
+                "Insert symbol or FFXIV icon"))
+        {
+            _symbolPicker.OpenPopup();
+        }
+        var insertedSymbol = _symbolPicker.DrawAndConsume();
+        if (insertedSymbol is not null)
+        {
+            // Same cursor-aware splice idiom as the AutoComplete commit path at
+            // ChatLogWindow.cs:2487-2493. Clamp because CursorPos can drift if
+            // the user mutates Chat while the popup is open.
+            var pos = Math.Clamp(CursorPos, 0, Chat.Length);
+            Chat = Chat[..pos] + insertedSymbol + Chat[pos..];
+            Activate = true;
+            ActivatePos = pos + insertedSymbol.Length;
+        }
+        ImGui.SameLine();
+
         var beforeIcon = ImGui.GetCursorPos();
 
         var tintSelector = Plugin.Config.ColorSelectedInputChannelButton && inputColour.HasValue;