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

[vincentkoc]

Summary

• register OpenClaw as a first-class compiled-in ACP runtime
• install the OpenClaw CLI through Buzz's managed npm prefix
• require the self-contained ACP contract reported by openclaw acp info
• route model authentication through OpenClaw's normal configuration command
• remove the legacy Gateway-backed preset so there is one canonical runtime path

Buzz does not start, configure, or connect to an OpenClaw Gateway. It launches
one self-contained ACP stdio process and supplies the dedicated inherited
BUZZ_* identity to that process.

Stack

1. feat(desktop): enforce managed ACP runtime contracts #4238 adds generic runtime contract,
   installation, status, and spawn-boundary enforcement.
2. This PR adds only the OpenClaw catalog and product integration on top.

GitHub cannot use a branch from a read-only fork as an upstream PR base. Until
#4238 merges, the exact incremental upper diff is:

vincentkoc/buzz@feat/managed-acp-runtime-contracts...feat/openclaw-acp-runtime

After #4238 merges, this PR's diff collapses to the upper commit automatically.

Related issue

• Managed agents: add Hermes, Kimi Coding, OpenCode and OpenClaw runtime adapters #3696

OpenClaw dependency chain

Do not merge or ship this PR until these OpenClaw changes are 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 they still expose the Gateway-backed ACP bridge.

Testing

• cargo test openclaw in desktop/src-tauri (1 passed)
• cargo test -p buzz-acp openclaw (1 passed)
• focused Desktop unit tests (125 passed)
• focused onboarding and logo tests after review fixes (31 passed)
• pnpm build:e2e
• Playwright tests/e2e/harness-management.spec.ts (15 passed)
• cargo fmt --check
• autoreview: accepted findings fixed; remaining release-order warning is the
  explicit draft merge gate above

Real Buzz/OpenClaw round-trip proof remains blocked on dedicated QA credentials:
two non-human Buzz identities plus an authorized room. Human owner/admin keys
must not be used.

[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?

[vincentkoc]

split as requested.

• generic install/verify/spawn-boundary layer: feat(desktop): enforce managed ACP runtime contracts #4238
• OpenClaw-only upper layer: this branch's second commit
• exact incremental upper diff: vincentkoc/buzz@feat/managed-acp-runtime-contracts...feat/openclaw-acp-runtime

GitHub cannot select a fork branch as the base of an upstream PR, so #3868 must
temporarily show the combined stack. Once #4238 merges, this PR becomes the
OpenClaw-only diff without another rewrite.