Allow expanding collapsed multi-line paste in input prompt

Request

When pasting multi-line text into the Claude Code prompt, it collapses to [Pasted text #N +M lines]. There's no way to expand this inline to see or edit the pasted content before submitting.

Use case

During interactive workflows (e.g., editing a draft Slack message), users paste multi-line replacement text and want to verify it looks correct before pressing Enter. Currently the only option is to blindly submit or use an external editor.

Suggested implementation

• Click or keybinding (e.g., Ctrl+P or Tab) to toggle between collapsed and expanded view of pasted text
• Or show the first 3-5 lines with a "show more" indicator

Current workaround

Ctrl+E to open in $EDITOR, but this doesn't appear to work in all environments (e.g., cmux terminal).