Refactor path normalization logic in RefinePathname module

- Extract path separator normalization logic from to_posix method to a private constant NORMALIZE_FILE_SEPARATOR.
- Apply NORMALIZE_FILE_SEPARATOR in the to_posix method and eql? method for consistent path normalization.
- Ensure NORMALIZE_FILE_SEPARATOR is private to the RefinePathname module to encapsulate the implementation details.

bin/ocran

@@ -7,6 +7,13 @@ module Ocran
   # The Pathname class in Ruby is modified to handle mixed path separators and
   # to be case-insensitive.
   module RefinePathname
+    NORMALIZE_FILE_SEPARATOR = if File::ALT_SEPARATOR
+                                 proc { |s| s.tr(File::ALT_SEPARATOR, File::SEPARATOR) }
+                               else
+                                 proc { |s| s }
+                               end
+    private_constant :NORMALIZE_FILE_SEPARATOR
+
     # Compares two paths for equality based on the case sensitivity of the
     # Ruby execution environment's file system.
     # If the file system is case-insensitive, it performs a case-insensitive
@@ -21,11 +28,7 @@ module Ocran
     private :pathequal
 
     def to_posix
-      if File::ALT_SEPARATOR
-        to_s.tr(File::ALT_SEPARATOR, File::SEPARATOR)
-      else
-        to_s
-      end
+      NORMALIZE_FILE_SEPARATOR[to_s]
     end
 
     # Checks if two Pathname objects are equal, considering the file system's
@@ -35,8 +38,8 @@ module Ocran
     def eql?(other)
       return false unless other.is_a?(Pathname)
 
-      a = to_posix
-      b = other.to_posix
+      a = NORMALIZE_FILE_SEPARATOR[to_s]
+      b = NORMALIZE_FILE_SEPARATOR[other.to_s]
       pathequal(a, b)
     end