Allow customization of processing indicator text

Feature Request

Allow users to customize the processing indicator text (the word displayed while Claude is thinking/working) to a single word of their choice.

Use Case

Users may want to simplify or personalize the processing indicator. For example, displaying just "Working" instead of the default rotating messages.

Proposed Solution

Add a configuration option (via /config or settings file) to set a custom single-word processing indicator, e.g.:

{
  "processingIndicator": "Working"
}

Benefits

• Reduces visual distraction for users who prefer minimal UI
• Allows personalization of the CLI experience
• Simple to implement as a string configuration option