v0.0.57

• Introduce OllamaChat::StateSelectors module with StateSelector class for
  managing configurable states
• Replace simple string-based document policy and think mode with
  StateSelector objects
• Add allow_empty parameter to StateSelector#initialize method to allow
  empty states in voice output
• Update StateSelector#selected= to conditionally validate states based on
  allow_empty?
• Refactor voice handling to use StateSelector by replacing @current_voice
  with @voices StateSelector
• Update FollowChat to use @voices.selected instead of @current_voice for
  voice selection
• Simplify change_voice method in dialog.rb to delegate to @voices.choose
• Update voice display in information.rb to use @voices.show instead of raw
  voice name
• Update configuration format to support nested think settings with mode
  and loud sub-properties
• Modify command handlers to use document_policy.choose and
  think_mode.choose instead of legacy methods
• Update OllamaChat::Chat initialization to use setup_state_selectors
  method
• Refactor OllamaChat::ThinkControl to use new state selector system
• Update OllamaChat::Parsing to reference @document_policy.selected instead
  of @document_policy
• Update default configuration file to use format with nested think settings
• Add proper attr_reader for document_policy and think_mode state
  selectors
• Update help text to reference new state selector system
• Update OllamaChat::Switches to handle nested think configuration
• Add OllamaChat::StateSelectors to required files in lib/ollama_chat.rb