Feature request: inline reply/annotation with numbered references for chat responses

## Problem

Claude Code on the web already supports inline comments on diff lines: select a line, type feedback, it's bundled with the next message so Claude sees exactly what's being referenced.

General Claude.ai chat has no equivalent. When you select text in a response and reply to it, the excerpt is just copy-pasted into the input box as flat text, with no persistent link back to that part of the response.

## Feature request

1. When selecting text in a Claude response and choosing "reply," anchor the excerpt as a numbered reference (footnote-style) instead of a flat copy-paste.
2. Let the user write a comment tied to that specific excerpt, separate from other comments on the same response.
3. Apply the same numbering scheme to anything else added to the chat (pasted text, files, screenshots) so items can be referenced later (e.g. "ref [2]") by both user and Claude.

## Comparable existing behavior

- Claude Code (web): inline comments on diff lines, bundled into next message.
- Claude Design: click-to-comment on canvas elements.
- Cursor: select text in a response, "copy to chat," comment inline.

This request is to bring the diff-line-comment pattern (or something close to it) to the general chat surface, with numbering that persists across the whole conversation rather than resetting per message.

## Use case

Reviewing long, multi-part responses and giving precise, section-specific feedback instead of one undifferentiated comment on the entire message

The issue names no repository files, tests, or entry points. First confirm whether the requested behavior belongs in Claude Code or another product surface, then define acceptance checks for numbered references, separate comments, persistent conversation-wide numbering, and references for pasted text, files, and screenshots.

Written by the indexing model from the issue text.