docs(acp): document Buzz host integration

[NYTEMODEONLY]

Summary

• document Buzz as an ACP host for an existing Hermes Agent
• show the buzz-acp -> hermes acp runtime topology and minimal launch configuration
• explain dedicated Buzz identities, channel-scoped access, secret handling, and headless permission risk
• document the relay-directory profile that makes a hosted Hermes identity discoverable under Agents → External agents
• document owner-only Buzz presentation customization across cards, profiles, messages, mentions, DMs, and sidebars
• document BUZZ_ACP_RELAY_OBSERVER=true for encrypted owner Activity telemetry
• add an end-to-end verification flow for identity, avatar propagation, signed replies, and live Activity
• link to the full Buzz operator guide for persistent systemd deployment and troubleshooting

Why

Hermes already exposes a native ACP server, and Buzz accepts arbitrary ACP agents over stdio. The integration works end to end without a Hermes core change:

Buzz relay <-- WebSocket --> buzz-acp <-- ACP over stdio --> Hermes Agent

Documenting the completed lifecycle in the existing ACP host guide gives Hermes users a supported path to collaborative Buzz channels while preserving their current provider configuration, Soul, prompts, memory, skills, tools, and identity.

This remains an ACP interoperability guide at the edge of Hermes. It adds no core tool, platform adapter, plugin, dependency, prompt surface, or Hermes-owned setting. Buzz presentation and observer settings live in the bridge/owner client.

Live end-to-end proof

The flow is deployed on a supervised Linux VPS using an existing Hermes Agent:

• hermes acp --check returned OK
• buzz-acp initialized Hermes and loaded its existing memory and native tools
• the dedicated identity joined a Buzz channel and appeared in the real owner client under External agents
• an owner-selected avatar propagated across the card, profile, channel post, and DM sidebar
• BUZZ_ACP_RELAY_OBSERVER=true enabled encrypted owner-addressed kind 24200 activity
• a fresh Hermes turn produced a signed Buzz reply and a complete owner-decrypted Activity transcript
• the owner-side archive captured 11 signed observer frames for that live turn
• Hermes-owned runtime state was not modified

No private key, API token, owner authorization, private community endpoint, or owner-addressed event identifier is included in this change.

Validation

At head:

• npm run build in website/
  • English and zh-Hans production builds completed successfully
  • the build reports existing unrelated link and anchor warnings elsewhere in the documentation tree
• git diff --check
• required Co-authored-by and Signed-off-by trailers are present

Related upstream

• Buzz runtime support and operator documentation:
  feat(agents): add Hermes ACP and external-agent integration block/buzz#2468

[teknium1]

Merged via PR #73571 with your authorship preserved on both commits. During salvage we re-verified each claim against the block/buzz source: the env vars, kind-24200/NIP-AO observer frames, and the auto-subscribe channel model all checked out and are in the published docs; we dropped the pieces we couldn't verify upstream (the docs/hermes-agent-acp.md link 404s in block/buzz, and the relay-directory/External-agents walkthrough), swapped in the buzz-admin key-minting flow from the buzz-acp README, cross-linked the relay-bridge and Buzz-Desktop sections, and added the zh-Hans translation. Thanks for mapping this integration path end to end — the live E2E writeup made verification much easier.