Add ability to expand and edit collapsed pasted text in the prompt

Problem

When a large block of text is pasted into the prompt, Claude Code collapses it into a placeholder like [Pasted text +N lines]. There is no way to expand, view, or edit that content before sending.

The external editor (Ctrl+G / Ctrl+X Ctrl+E) does not solve this — it opens the prompt buffer containing only the placeholder token, not the actual pasted content. So the pasted text is effectively frozen: it cannot be inspected, trimmed, or corrected once pasted. The only workarounds are re-pasting into an external file or reading it back via ! cat, both of which are clumsy.

Requested behavior

Provide a way to expand a collapsed paste in place and edit it, similar to virtually every other text-input surface:

• A command/keybinding to expand the placeholder into the editable buffer, or
• Have the external editor (Ctrl+G) inject the real pasted content rather than the placeholder token, so it can be edited and saved back.

Why

Pasted content is frequently the thing that needs the most editing (removing secrets, trimming irrelevant lines, fixing a bad copy). Freezing it as an opaque blob defeats the purpose of an interactive prompt.

Environment

• Claude Code CLI, Windows 11, PowerShell