feat(api): add computer use to beta agents (#3989)

## Summary

Adds typed computer-use tools, approval responses, screenshots, and
desktop settings to beta.agents.

## Changes

- Support computer_use tools and optional screenshots.
- Add browser authentication and origin-access approval inputs and
required actions.
- Expose computer-use calls and credential-free approval history.
- Add desktop settings for hosted environments and environment
templates.

Co-authored-by: marcuswood-oai <323319819+marcuswood-oai@users.noreply.github.com>