Add draw support for loading external DSL path files

[kalashnikovisme]

Motivation

• Allow reusable path trees to be authored in separate Ruby DSL files and loaded into a client with a simple draw 'relative/path' call so nested path/response/root_method declarations can be kept in external files.

Description

• Added draw(file_name) to Purple::Client which resolves file_name relative to the caller file, auto-appends .rb when missing, and evaluates the file in the client class context via instance_eval.
• The draw helper raises clear LoadError messages when the caller file cannot be detected or when the target DSL file does not exist.
• Added a unit-spec fixture file spec/purple/support/drawn_client/v1.rb which declares a v1/warehouses path and response schema.
• Added DrawnClient and a new RSpec case in spec/purple/client_spec.rb which uses draw 'support/drawn_client/v1' and asserts the generated warehouses root method invokes the correct URL and returns the parsed response.

Testing

• Attempted bundle exec rspec spec/purple/client_spec.rb, but it could not run because the rspec executable/gems were not available in this environment.
• Attempted bundle install, but the install was blocked by a network 403 Forbidden from rubygems.org in this environment.
• Performed syntax checks with ruby -c lib/purple/client.rb, ruby -c spec/purple/client_spec.rb, and ruby -c spec/purple/support/drawn_client/v1.rb, and all returned Syntax OK.

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Codex Task