Add clarifying comments for ig parameter

The ig (ignore instance) is loaded once from .gitignore and passed
through recursion for efficiency. This avoids re-parsing .gitignore
at every directory level.

Author: ammar-agent

src/services/tools/file_list.ts

@@ -17,8 +17,8 @@ interface TraversalOptions {
   pattern?: string;
   useGitignore: boolean;
   maxEntries: number;
-  ig: ReturnType<typeof ignore> | null;
-  rootPath: string;
+  ig: ReturnType<typeof ignore> | null; // Ignore instance loaded once from .gitignore, reused across recursion
+  rootPath: string; // Root path for calculating relative paths in gitignore matching
 }
 
 interface TraversalResult {