fix: correct Kotlin comment node kind and resolve clippy warnings

- Replace "multiline_comment" with "block_comment" in Kotlin parser
- Add new() methods to CompressedFileStorage and FileStorage
- Implement Default trait for FileStorage
- Update snapshot test for Kotlin comprehensive extraction

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: unhappychoice

src/domain/models/languages/kotlin.rs

@@ -26,6 +26,6 @@ impl Language for Kotlin {
 
     fn is_valid_comment_node(&self, node: tree_sitter::Node) -> bool {
         let node_kind = node.kind();
-        node_kind == "line_comment" || node_kind == "multiline_comment"
+        node_kind == "line_comment" || node_kind == "block_comment"
     }
 }

src/domain/repositories/challenge_repository.rs

@@ -39,14 +39,14 @@ impl ChallengeRepository {
 
         Self {
             cache_dir,
-            storage: CompressedFileStorage::default(),
+            storage: CompressedFileStorage::new(),
         }
     }
 
     pub fn with_cache_dir(cache_dir: PathBuf) -> Self {
         Self {
             cache_dir,
-            storage: CompressedFileStorage::default(),
+            storage: CompressedFileStorage::new(),
         }
     }
 

src/infrastructure/storage/compressed_file_storage.rs

@@ -19,6 +19,10 @@ mod real_impl {
     impl AppDataProvider for CompressedFileStorage {}
 
     impl CompressedFileStorage {
+        pub fn new() -> Self {
+            Self
+        }
+
         /// Save compressed binary data to a file
         pub fn save<T: Serialize>(&self, file_path: &Path, data: &T) -> Result<()> {
             // Ensure parent directory exists
@@ -130,6 +134,10 @@ mod mock_impl {
     impl AppDataProvider for CompressedFileStorage {}
 
     impl CompressedFileStorage {
+        pub fn new() -> Self {
+            Self::default()
+        }
+
         pub fn save<T: Serialize>(&self, file_path: &Path, data: &T) -> Result<()> {
             use flate2::{write::GzEncoder, Compression};
             use std::io::Write;

src/infrastructure/storage/file_storage.rs

@@ -20,6 +20,12 @@ mod real_impl {
 
     impl AppDataProvider for FileStorage {}
 
+    impl Default for FileStorage {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
     impl FileStorage {
         pub fn new() -> Self {
             Self

tests/integration/languages/snapshots/r#mod__integration__languages__extractor__test_kotlin_comprehensive_extraction.snap

@@ -11,6 +11,10 @@ expression: "serde_json::to_string_pretty(&snapshot_data).unwrap()"
           1,
           16
         ],
+        [
+          17,
+          36
+        ],
         [
           64,
           77