feat(themes): add an export button for the active theme

HellionChat/Ui/Components/Settings/ThemeImportExportRow.cs

@@ -37,6 +37,12 @@ internal sealed class ThemeImportExportRow
             OpenThemesFolder();
         }
 
+        ImGui.SameLine();
+        if (ImGui.Button("Export active theme…"))
+        {
+            ExportActive();
+        }
+
         ImGui.SetNextItemWidth(-1);
         ImGui.InputTextWithHint(
             "##theme-import-path",
@@ -293,4 +299,43 @@ internal sealed class ThemeImportExportRow
             _logger.LogWarning(ex, "Could not open themes folder {Dir}", dir);
         }
     }
+
+    private void ExportActive()
+    {
+        // Capture the active theme now, not in the async dialog callback — the user
+        // could switch themes while the dialog is open.
+        var theme = _themes.Active;
+        var defaultName = $"{theme.Slug}.json";
+
+        Plugin.FileDialogManager.SaveFileDialog(
+            "Export theme",
+            ".json",
+            defaultName,
+            ".json",
+            (ok, path) =>
+            {
+                if (ok)
+                {
+                    ExportTo(theme, path);
+                }
+            },
+            null,
+            isModal: true
+        );
+    }
+
+    private void ExportTo(Theme theme, string path)
+    {
+        try
+        {
+            var json = ThemeJsonWriter.Serialize(theme);
+            File.WriteAllText(path, json);
+            _logger.LogInformation("Exported theme {Slug} to {Path}", theme.Slug, path);
+        }
+        catch (Exception ex)
+            when (ex is IOException or UnauthorizedAccessException or SecurityException)
+        {
+            _logger.LogWarning(ex, "Theme export to {Path} failed", path);
+        }
+    }
 }