Feature: WaitingIndicator tool for visual 'waiting for input' signal

Summary

When Claude finishes a response with a question or needs user input, there's no visual distinction between "Claude is talking" and "Claude is waiting for your answer." The AskUserQuestion tool provides this visual distinction, but it forces a rigid multiple-choice format that doesn't fit many conversational situations (open-ended discussions, simple yes/no, "any changes?").

Related to #21894 (prompt-level state indicators), but this is specifically about a tool Claude can call to signal it's waiting.

Proposal

A lightweight WaitingIndicator tool (or similar) that Claude can call at the end of a response to visually signal "I'm waiting for your input." No structured options required — just a visual treatment that makes it obvious the ball is in the user's court.

Use cases

• After presenting a draft: "Let me know if this looks good or what to change."
• During a discussion: "What do you think?"
• After answering a question: waiting for follow-up

Why not AskUserQuestion?

• Forces 2-4 discrete options — doesn't fit open-ended questions
• Annoying when used repeatedly in quick succession
• Often the user wants to type freely, not pick from a menu
• Users end up rejecting the prompt just to type their real answer

Why not just text?

• Plain text questions at the end of a response blend into the output
• Users scanning quickly can miss that Claude is waiting
• Especially problematic with long responses where the question is at the bottom

Possible implementation

• A tool call that renders a subtle visual indicator (colored bar, icon, status badge) below the response
• Could be as simple as a distinct "awaiting input" state on the prompt line
• No parameters needed, or optional message parameter for the waiting prompt text