Ruby: Extract Herb#ensure_installed helper

[marcoroth]

This pull request extracts a shared Herb.ensure_installed helper that handles inline gem installation via Bundler.

Previously, both RenderAnalyzer and Project duplicated the same bundler/inline gemfile block with identical boilerplate for requiring, installing, and suppressing Ruby warnings during gem activation.

The new helper centralizes this into a single method on the Herb module, making call sites one-liners and suppressing the noisy RDoc constant redefinition warnings that bundler/inline triggers in some environments:

❯ bundle exec herb actionview graph app/views/profiles/_header.html.erb

 Herb 🌿 v0.9.7

 Building render graph...
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc/version.rb:8: warning: already initialized constant RDoc::VERSION
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc/version.rb:8: warning: previous definition of VERSION was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:68: warning: already initialized constant RDoc::VISIBILITIES
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:68: warning: previous definition of VISIBILITIES was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:74: warning: already initialized constant RDoc::DOT_DOC_FILENAME
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:74: warning: previous definition of DOT_DOC_FILENAME was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:79: warning: already initialized constant RDoc::GENERAL_MODIFIERS
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:79: warning: previous definition of GENERAL_MODIFIERS was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:84: warning: already initialized constant RDoc::CLASS_MODIFIERS
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:84: warning: previous definition of CLASS_MODIFIERS was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:89: warning: already initialized constant RDoc::ATTR_MODIFIERS
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:89: warning: previous definition of ATTR_MODIFIERS was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:94: warning: already initialized constant RDoc::CONSTANT_MODIFIERS
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:94: warning: previous definition of CONSTANT_MODIFIERS was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc.rb:99: warning: already initialized constant RDoc::METHOD_MODIFIERS
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc.rb:99: warning: previous definition of METHOD_MODIFIERS was here
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.0.3/lib/rdoc/markdown.rb:257: warning: already initialized constant RDoc::Markdown::KpegPosInfo
/Users/marcoroth/.local/share/mise/installs/ruby/4.0.0/lib/ruby/gems/4.0.0/gems/rdoc-7.2.0/lib/rdoc/markdown.rb:257: warning: previous definition of KpegPosInfo was here

Might be related to #1435

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@1665

npx https://pkg.pr.new/@herb-tools/language-server@1665

npx https://pkg.pr.new/@herb-tools/linter@1665

commit: e5d2dea

[github-actions]

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