Feature request: Up arrow should recall previous prompts in the composer

## Feature request

Support using the Up arrow in the chat composer to recall previous messages/prompts.

## Problem

In the current chat experience, I can't use the Up arrow to quickly reuse or edit previous prompts.

This makes iterative prompting slower, especially when I want to:
- resend a similar request with a small tweak
- recover a previous prompt after a failed run
- refine a long prompt without retyping it

## Requested behavior

When the composer is focused and the cursor is at the start of the input (or the input is empty), pressing the Up arrow should:
- recall the previous submitted prompt
- allow stepping back through prompt history
- ideally allow Down arrow to move forward again

## Why this matters

This is standard and very useful behavior in terminal/chat workflows. It makes iterative agent use much faster and reduces friction during debugging and prompt refinement.

## Nice-to-have details

- only trigger history recall when appropriate (for example not when navigating inside multiline text)
- preserve draft text when stepping through history, if possible
- scope history per chat/session rather than globally

No files or tests are identified in the issue. Start by locating the VS Code chat composer and its prompt-submission handling, then trace where chat or session state is kept; done means Up recalls earlier prompts, Down moves forward when applicable, and multiline editing is not disrupted.

Written by the indexing model from the issue text.