feat: skip similar pairs where path contains thumbnail/thumbnails

- Filters out thumbnail-vs-original false positives
- Only applies to pairs (group size 2)
- Case-insensitive path check
- New test: similar_pair_with_thumbnail_path_ignored
- 25 tests passing

src/lib.rs

@@ -174,6 +174,13 @@ pub fn find_duplicate_groups_with_size_ratio(
         if paths.len() > 1 {
             let non_exact = paths.iter().filter(|p| !exact_paths.contains(*p)).count();
             if non_exact >= 2 {
+                // Skip pairs where a thumbnail path is involved
+                if paths.len() == 2 && paths.iter().any(|p| {
+                    let s = p.to_string_lossy().to_ascii_lowercase();
+                    s.contains("thumbnail") || s.contains("thumbnails")
+                }) {
+                    continue;
+                }
                 groups.push(DuplicateGroup {
                     kind: DuplicateKind::Similar,
                     paths,
@@ -351,4 +358,15 @@ mod tests {
         assert!(groups2.iter().any(|g| g.kind == DuplicateKind::Similar),
             "files with similar sizes should be grouped");
     }
+
+    #[test]
+    fn similar_pair_with_thumbnail_path_ignored() {
+        let entries = vec![
+            make_entry_sized("/photos/cat.jpg", "aaa", 0b0000_0000, 100_000),
+            make_entry_sized("/photos/.thumbnails/cat.jpg", "bbb", 0b0000_0001, 95_000),
+        ];
+        let groups = find_duplicate_groups(&entries, 8);
+        assert!(!groups.iter().any(|g| g.kind == DuplicateKind::Similar),
+            "similar pair where one path contains 'thumbnails' should be ignored");
+    }
 }