feat(desktop): add Cybara ACP harness preset

## Problem

Cybara exposes a native ACP v1 server through `cybara acp`, but Buzz does not include it in the built-in harness gallery. Users can configure it manually through Bring Your Own Harness, but discovery and setup guidance are not automatic.

## Proposed solution

Add Cybara as a tier-2 preset harness using the existing data-driven preset catalog:

- command: `cybara`
- arguments: `acp`
- install guide: `https://cybara.ai/download#cli-tui`
- PATH-based availability discovery
- bundled MIT-licensed Cybara mark with provenance
- catalog and logo regression coverage

Cybara already keeps ACP protocol frames on stdout and diagnostics on stderr, accepts Buzz initialization/session creation, and falls back cleanly through Buzz's ACP v1 compatibility path. No runtime-specific frontend or spawn logic should be necessary.