Indexing exclusions are ignored with the Rubydex indexer (0.27.0.beta5) #4253

Summary

With the Rubydex indexer (0.27.0.beta5), there is no working way to reduce what
gets indexed. The documented initializationOptions.indexing settings
(excludedGems, excludedPatterns, includedPatterns) have no effect, and
because indexing now covers every locked gem, startup is dominated by vendored
gem code.

Environment

• Ruby LSP 0.27.0.beta5 (--beta), gem rubydex 0.4.4
• Neovim 0.12.4, launched through a per-project Ruby (rv), composed .ruby-lsp bundle
• Project: Rails 8.1 app, Ruby 4.0.0, bundle at vendor/bundle, 189 gems

Reproduction

1. Launch the server against a project with a vendored bundle.
2. Send initialize with initializationOptions: { indexing: { excludedGems: ["<gem>"] } }.
3. Compare the index contents with a run that omits the option — identical.

An excluded gem is still indexed, so exclusion cannot be used to cut startup time.

Expected

excludedGems / excludedPatterns from the documented initialization options
removes those files from the index, as they did with RubyIndexer.

Actual

The options are ignored entirely with the Rubydex indexer.

Evidence

1. Nothing in ruby_lsp/ under 0.27.0.beta5 reads the indexing options. The
   only occurrences are progress notifications and
   perform_initial_indexing, which calls graph.index_workspace unconditionally:

   benchmark("index_workspace") { @global_state.graph.index_workspace }
   benchmark("full_resolve") { @global_state.graph.resolve }

2. rubydex.toml has no index section; adding one fails:

   Rubydex::ConfigError: Invalid config file .../rubydex.toml: unknown section `index`
   

   The Ruby config API only models [linter].
3. Rubydex::Graph exposes no setter in 0.4.4:

   NoMethodError: undefined method 'exclude_patterns=' for an instance of Rubydex::Graph
   

4. Graph#workspace_paths seeds the index from every top-level workspace
   directory plus each locked gem's require paths, with no group filtering:

   specs = Bundler.locked_gems&.specs
   specs.each do |lazy_spec|
     spec = Gem::Specification.find_by_name(lazy_spec.name)
     spec.require_paths.each { |path| paths << File.join(spec.full_gem_path, path) }
   end

   This also means development and test gems are indexed again, whereas Automatically exclude transitive test dependencies from indexing #1078
   excluded development and transitive development dependencies.

Measured impact

On a Rails 8 project with a vendored bundle:

The cost is paid once per server process, since the graph is not cached to disk
(see #1009), and 95% of it is gem code from vendor/bundle.

Suggestion

Either honor initializationOptions.indexing.excludedGems / excludedPatterns
in the Rubydex path, or restore the previous behavior of skipping development
and test groups. Both would cut startup substantially for vendored bundles.