chore: update rubocop gem

[dpep]

Description 📖

This pull request brings the lint gems current — rubocop 1.70.0 → 1.88.2 and standard 1.44.0 → 1.56.0 — and fixes the one offense the upgrade surfaces.

TargetRubyVersion and the standard: config/ruby-3.0.yml inherit are deliberately left alone, so this is a tool bump only and no new cops are gated on the Ruby target.

Background 📜

Both gems are declared unversioned in the Gemfile, so this is a Gemfile.lock update. The dependency changes are confined to rubocop's own tree: rubocop-ast, rubocop-minitest, rubocop-performance, standard-performance, parser, json, ast, parallel, regexp_parser, language_server-protocol and unicode-display_width. standard 1.56.0 requires rubocop ~> 1.88.0, which is what pulls rubocop forward.

The upgrade reports exactly one offense, Style/RedundantArrayFlatten in ViteRuby::CLI::FileUtils.write:

vite_ruby/lib/vite_ruby/cli/file_utils.rb:17:34: C: Style/RedundantArrayFlatten: Remove the redundant flatten.

It is a true positive — Array#join already joins nested arrays recursively, so flattening first is redundant.

The Fix 🔨

By dropping the flatten, and adding a test that pins the nested-content contract of write.

The cop is marked Safe: false, so rubocop -a skips it and rubocop -A was not used; the one-line change is applied by hand.

Verified rather than assumed:

• The new test_write_nested_content passes both with and without the flatten, so it pins the documented behaviour of write rather than the implementation.
• Checked the two expressions agree across the shapes this call site can receive — flat strings, nested arrays, deeper nesting, nil elements, an empty list and a hash.
• bundle exec rubocop is clean: 101 files, no offenses (it reported 1 before the fix).
• bin/rake test passes on Ruby 4.0.6: 115 tests, 437 assertions, 0 failures.

Two pre-existing notices now surface with the newer rubocop, left out to keep this focused: Naming/PredicateName has been renamed to Naming/PredicatePrefix, and rubocop-performance / rubocop-minitest now prefer plugins: over require:. Both are warnings only and the run still exits 0. Happy to fold either in, or follow up separately, whichever you prefer.