Feature request: Shift+Arrow text selection in prompt input

Summary

Add support for standard Shift+Arrow text selection in the prompt input box, similar to any modern text editor.

Current behavior

The prompt input supports word-wise navigation/deletion (Alt+B, Alt+F, Ctrl+W, Ctrl+K, Ctrl+U), but there is no way to visually select a range of text and then replace or delete it. Selection actions (selection:extendLeft, etc.) exist but only apply to the Scroll context, not the input box.

Requested behavior

In the prompt input:

• Shift+Left / Shift+Right — extend selection by character
• Ctrl+Shift+Left / Ctrl+Shift+Right — extend by word
• Shift+Home / Shift+End — extend to line edges
• Shift+Up / Shift+Down — extend by line (for multi-line prompts)
• Typing / Backspace / Delete / paste replaces the selection

Configurability via ~/.claude/keybindings.json would be a plus.

Why

Editing long or multi-line prompts is currently tedious — the only way to replace a phrase mid-prompt is to repeatedly Ctrl+W or manually backspace. Shift+Arrow selection is muscle memory for most developers and would significantly improve prompt authoring ergonomics.

Environment

Claude Code on Windows 11, running inside the VS Code integrated terminal. Same behavior reported from Windows Terminal.