fix: support case-insensitive file matching on Windows

On Windows, file paths are case-insensitive, so pattern matching should
be case-insensitive as well. This fix normalizes both patterns and paths
to lowercase on Windows before matching, while maintaining case-sensitive
behavior on Unix systems.

Changes:
- Convert patterns to lowercase during normalization on Windows
- Convert normalized paths to lowercase before matching on Windows
- Use conditional compilation (#[cfg(target_os = "windows")])
- Add #[cfg_attr] to silence unused_mut warnings on non-Windows

Fixes the test_case_insensitivity_windows test failure.

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

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

Author: Boshen

src/tsconfig/file_matcher.rs

@@ -114,7 +114,15 @@ impl TsconfigFileMatcher {
     fn normalize_patterns(patterns: Vec<String>, tsconfig_dir: &Path) -> Vec<String> {
         patterns
             .into_iter()
-            .flat_map(|pattern| {
+            .flat_map(|
+                #[cfg_attr(not(target_os = "windows"), allow(unused_mut))]
+                mut pattern
+            | {
+                // On Windows, convert to lowercase for case-insensitive matching
+                #[cfg(target_os = "windows")]
+                {
+                    pattern = pattern.to_lowercase();
+                }
                 // Convert absolute to relative
                 #[allow(clippy::option_if_let_else)] // map_or would cause borrow checker issues
                 let pattern = if Path::new(&pattern).is_absolute() {
@@ -180,11 +188,18 @@ impl TsconfigFileMatcher {
     pub fn matches(&self, file_path: &Path) -> bool {
         // Normalize path for matching
         #[allow(clippy::manual_let_else)] // Match is clearer here
-        let normalized = match self.normalize_path(file_path) {
+        #[cfg_attr(not(target_os = "windows"), allow(unused_mut))]
+        let mut normalized = match self.normalize_path(file_path) {
             Some(p) => p,
             None => return false, // Path can't be normalized
         };
 
+        // On Windows, convert to lowercase for case-insensitive matching
+        #[cfg(target_os = "windows")]
+        {
+            normalized = normalized.to_lowercase();
+        }
+
         // 1. Check files array first (absolute priority)
         if let Some(files) = &self.files {
             for file in files {