test(rust): a file named like a sample folder is refused, nothing created (#384)

Review 25592, point 1: the pre-check reads exists(), not is_dir(); under
is_dir() a file named "Exemple Tangerine" let "Exemple Desjardins" be
created before create_dir failed with a raw "File exists". The
reviewer's test pins it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src-tauri/src/commands/fs_commands.rs

@@ -456,6 +456,23 @@ mod sample_folder_tests {
         assert_eq!(entries, 1, "nothing but the existing folder");
     }
 
+    /// A FILE named like a sample folder blocks it as well (#384 review): the
+    /// check reads `exists()`, not `is_dir()`, so nothing is half-created and
+    /// the refusal keeps its code instead of a raw "File exists" from
+    /// `create_dir`.
+    #[test]
+    fn refuses_a_file_named_like_a_sample_folder_and_writes_nothing() {
+        let dir = sandbox("file-tangerine");
+        fs::write(dir.join(SAMPLE_TANGERINE_FOLDER), "").unwrap();
+        let result = create_sample_import_folders(as_arg(&dir), "2026-09-25".to_string());
+        let desjardins_created = dir.join(SAMPLE_DESJARDINS_FOLDER).exists();
+        let entries = fs::read_dir(&dir).unwrap().count();
+        cleanup(&dir);
+        assert_eq!(result.unwrap_err(), "sample_folder_exists:Exemple Tangerine");
+        assert!(!desjardins_created, "Exemple Desjardins must not be created");
+        assert_eq!(entries, 1, "nothing but the existing file");
+    }
+
     #[test]
     fn writes_both_folders_for_the_two_previous_months() {
         let dir = sandbox("success");