fix: restore listen gem in Gemfile.lock for CI compatibility

Remove conditional Ruby version check for listen gem to ensure
Gemfile.lock contains the dependency for all Ruby versions.

Author: yhk1038

Gemfile

@@ -13,6 +13,7 @@ group :development, :test do
   gem "simplecov", "~> 0.22.0", require: false
   gem "simplecov-lcov", "~> 0.8.0", require: false
 
-  # listen gem for watch mode - skip on Ruby 4.0+ due to ffi compatibility
-  gem "listen", "~> 3.8" if RUBY_VERSION < "4.0"
+  # listen gem for watch mode
+  # Note: May have compatibility issues on Ruby 4.0+ due to ffi
+  gem "listen", "~> 3.8"
 end

Gemfile.lock

@@ -12,9 +12,14 @@ GEM
     benchmark (0.5.0)
     diff-lcs (1.6.2)
     docile (1.4.1)
+    ffi (1.17.3)
+    ffi (1.17.3-x86_64-linux-gnu)
     json (2.17.1)
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
+    listen (3.9.0)
+      rb-fsevent (~> 0.10, >= 0.10.3)
+      rb-inotify (~> 0.9, >= 0.9.10)
     logger (1.7.0)
     parallel (1.27.0)
     parser (3.3.10.0)
@@ -24,6 +29,9 @@ GEM
     racc (1.8.1)
     rainbow (3.1.1)
     rake (13.3.1)
+    rb-fsevent (0.11.2)
+    rb-inotify (0.11.1)
+      ffi (~> 1.0)
     rbs (3.10.0)
       logger
     regexp_parser (2.11.3)
@@ -74,6 +82,7 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  listen (~> 3.8)
   rake (~> 13.0)
   rbs (~> 3.0)
   rspec (~> 3.0)