feat(desktop): add OpenClaw as a first-class ACP runtime

[vincentkoc]

Summary

• add OpenClaw to Buzz Desktop's first-class ACP runtime catalog
• install it through Buzz's private managed Node/npm prefix without owning any OpenClaw service lifecycle
• require the self-contained ACP contract reported by openclaw acp info
• re-verify the exact executable at the shared spawn boundary before launching buzz-acp
• route model setup through OpenClaw's ACP terminal-auth method
• remove the stale OpenClaw preset so there is one canonical runtime path

This deliberately does not start, configure, or connect to an OpenClaw Gateway. Buzz launches one self-contained ACP stdio runtime and supplies the normal inherited BUZZ_* environment.

Related issue

• Managed agents: add Hermes, Kimi Coding, OpenCode and OpenClaw runtime adapters #3696
• related launch-argument fix: fix(acp): launch ACP/stdio mode for managed agents with no runtime preset #3804

Dependency chain

Do not merge or ship this PR until these draft OpenClaw PRs are ready and released:

1. refactor(acp): run inbound sessions locally openclaw/openclaw#116678
2. feat(acp): advertise the self-contained host contract openclaw/openclaw#116690

Current released OpenClaw builds are intentionally classified as incompatible because their ACP command still depends on a separately running Gateway.

Testing

• cargo test managed_agents -- --nocapture (917 passed)
• cargo test discovery -- --nocapture (253 passed after the final probe consolidation)
• cargo test agent_auth -- --nocapture (19 passed)
• cargo test compatibility -- --nocapture (5 passed)
• cargo test cli_probe -- --nocapture (6 passed)
• cargo check in desktop/src-tauri
• pnpm test in desktop (3,879 passed before the final focused readiness adjustment)
• focused onboarding readiness tests (19 passed after the final adjustment)
• pnpm check
• pnpm build:e2e
• Playwright harness management suite (15 passed)
• cargo test -p buzz-acp setup_mode::tests
• git diff --check
• autoreview clean after the final state-machine changes

Real Buzz/OpenClaw round-trip proof remains blocked on dedicated QA credentials: two non-human Buzz identities plus an authorized room (driverPrivateKey, sutPrivateKey, relayUrl, and roomId). Human owner/admin keys must not be used. The acceptance run should remain a pre-merge requirement once those credentials and an OpenClaw release containing the dependency chain exist.

[Chessing234]

big surface. could you split the install/verify bits from the catalog entry so the scary spawn-boundary changes are easier to review alone?