fix: VC guard on filmstripActivePath, pickPrimary default case, cleanup

Issues found during code review:

- filmstripActivePath was missing the is_virtual_copy guard that
  variantOptions already had. A VC of a grouped file would highlight
  the group primary in the filmstrip instead of itself.
- pickPrimary switch had no default case. A corrupt settings file
  sending an unknown preference string would return undefined.
- Use Set for extension dedup in groupBadgeInfo (was indexOf loop).
- Add skip_serializing to deprecated group_associated_files so it
  stops being written back to the settings file.
- Remove stale comment.

Author: EnTeQuAk

src-tauri/src/file_management.rs

@@ -399,7 +399,7 @@ pub struct AppSettings {
     pub active_waveform_channel: Option<String>,
     /// Deprecated: grouping is now driven by the rawStatus filter.
     /// Kept for backward-compatible deserialization of existing settings.
-    #[serde(default)]
+    #[serde(default, skip_serializing)]
     pub group_associated_files: Option<bool>,
     #[serde(default)]
     pub group_preferred_type: Option<String>,

src/App.tsx

@@ -1050,15 +1050,12 @@ function App() {
     return buildImageGroups(imageList, groupPreferredType);
   }, [imageList, isGroupingActive, groupPreferredType]);
 
-  // Map from group_id to variant count, for rendering badges on thumbnails
   // Badge info for grouped thumbnails: count + label like "RAF+JPG"
   const groupBadgeInfo: Record<string, { count: number; label: string }> = useMemo(() => {
     if (!groupingResult) return {};
     const info: Record<string, { count: number; label: string }> = {};
     for (const [groupId, group] of groupingResult.groups) {
-      const extensions = group.variants
-        .map((v) => getVariantLabel(v.path))
-        .filter((ext, i, arr) => arr.indexOf(ext) === i); // dedupe
+      const extensions = [...new Set(group.variants.map((v) => getVariantLabel(v.path)))];
       info[groupId] = {
         count: group.variants.length,
         label: extensions.join('+'),
@@ -1087,7 +1084,7 @@ function App() {
     if (!selectedImage) return null;
     if (!groupingResult) return selectedImage.path;
     const imageFile = imageList.find((img) => img.path === selectedImage.path);
-    if (!imageFile?.group_id) return selectedImage.path;
+    if (!imageFile?.group_id || imageFile.is_virtual_copy) return selectedImage.path;
     const group = groupingResult.groups.get(imageFile.group_id);
     return group?.primary.path ?? selectedImage.path;
   }, [selectedImage?.path, groupingResult, imageList]);

src/utils/imageGrouping.ts

@@ -77,6 +77,8 @@ function pickPrimary(files: ImageFile[], preference: GroupPreference): ImageFile
       return raw ?? nonRaw ?? files[0];
     case 'jpeg':
       return nonRaw ?? raw ?? files[0];
+    default:
+      return files[0];
   }
 }