Fix edge case and timing issues in locale generation

1. Fixed critical edge case in files_are_outdated:
   - Changed to return false when locale_files is empty
   - Prevents generation of empty translation files when no source YAML exists
   - Previously returned true (outdated), which would trigger empty generation

2. Improved user message clarity:
   - Updated message to show exact rake task syntax
   - Changed from "Use force=true" to "Use 'rake react_on_rails:locale force=true'"
   - Helps users understand how to pass the parameter correctly

3. Fixed timing-dependent test flake:
   - Added 10ms sleep in spec to ensure different timestamps on fast filesystems
   - Prevents CI failures where file regeneration happens within same timestamp
   - Test was failing in CI due to mtime equality instead of greater-than

All tests pass and RuboCop clean.

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

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

Author: justin808

lib/react_on_rails/locales/base.rb

@@ -40,7 +40,8 @@ def initialize(force: false)
         return if i18n_dir.nil?
 
         if !force && !obsolete?
-          puts "Locale files are up to date, skipping generation. Use force=true to regenerate."
+          puts "Locale files are up to date, skipping generation. " \
+               "Use 'rake react_on_rails:locale force=true' to force regeneration."
           return
         end
 
@@ -64,7 +65,7 @@ def exist_files
       end
 
       def files_are_outdated
-        return true if locale_files.empty?
+        return false if locale_files.empty? # No source files = nothing to generate
 
         latest_yml = locale_files.map { |file| File.mtime(file) }.max
         earliest = exist_files.map { |file| File.mtime(file) }.min

spec/react_on_rails/locales_to_js_spec.rb

@@ -55,6 +55,9 @@ module ReactOnRails
           # Get initial mtime after first generation
           initial_mtime = File.mtime(translations_path)
 
+          # Sleep to ensure different timestamp on fast filesystems
+          sleep 0.01
+
           # Touch files to make them newer than YAML (up-to-date)
           future_time = Time.current + 1.minute
           FileUtils.touch(translations_path, mtime: future_time)