chore: update CI Ruby/Node versions and GitHub Actions

[madogiwa0124]

Summary

• The Ruby/Node versions used in CI were outdated, so this updates them
  • Bump .ruby-version from 3.3.6 to 4.0.6, drop EOL Ruby 3.1/3.2 from the ruby.yml matrix, and add 3.4/4.0
  • Add .node-version (24.19.0) and load it via node-version-file in both ruby.yml and js.yml for consistency
• Also updated GitHub Actions used across workflows to their latest major versions
  • actions/checkout, actions/setup-node: v4 → v7
  • pnpm/action-setup: v4 → v6
  • crawl.yml's actions/checkout stays on v4, since v5+ requires the node24 runtime, which is incompatible with the container's glibc 2.17
• Removed the single-value matrix blocks in js.yml/rubocop.yml that had no real effect; rubocop.yml now relies on ruby/setup-ruby's automatic .ruby-version detection
• Updated the experimental include entries (Rails 8.0.x / edge) in ruby.yml to use the newest Ruby (4.0), matching the original intent of pairing them with the latest available Ruby
• Bumped unicode-emoji/unicode-display_width in Gemfile.lock: unicode-emoji 4.0.4 restricted required_ruby_version to < 4.0, which broke bundle install on Ruby 4.0. These are transitive dev dependencies of rubocop/standard (not in any gemspec), so this has no effect on library consumers. The bump also happens to pull in Unicode 17 data; bin/rubocop still reports no offenses on this codebase after the update

Test plan

• Confirmed CI passes on a same-repo PR (chore: update CI Ruby/Node versions and GitHub Actions madogiwa0124/vite_ruby#1), including the Ruby 4.0 build matrix
• Confirm CI passes here as well
• crawl.yml is unchanged, so no impact there