hermes - 💡(How to fix) Fix Feature: ACP client mode — allow Hermes to connect to external ACP agents

Feature Request

What: Add ACP client mode to Hermes so it can act as a controller for external ACP agents (OpenCode, Claude Code, etc.).

Why: Currently hermes acp only runs as a server (waiting for editors/IDEs to connect). There is no way for Hermes to actively connect to and control external ACP agents. This prevents cross-harness orchestration.

Use case: An operator runs both Hermes (operator shell) and OpenCode (coding harness) simultaneously. Hermes should be able to spawn, delegate tasks to, and manage OpenCode's session via ACP — similar to how Claude Code delegates to subagents, but across separate processes/harnesses.

Proposed solution: Add a --connect <url> option to hermes acp:

hermes acp --connect http://localhost:4444  # connect to OpenCode ACP server

This makes Hermes an ACP client that can:

1. Spawn or attach to an external ACP agent
2. Send tasks/instructions via JSON-RPC
3. Receive results, tool calls, and permission requests back
4. Coordinate multi-agent workflows from a single Hermes session

Alternatives considered:

• ACP is an open standard (Apache 2.0, backed by Zed, JetBrains, and Google Gemini CLI). Leveraging it avoids building a proprietary bridge.
• The existing acp-delegate skill (issue #12396) connects Hermes-to-Hermes; this extends the same pattern to cross-harness.

Priority: High for multi-harness operators. Many users run Hermes + Claude Code/OpenCode in parallel with no coordination layer.