feat: add Hermes agent plugin for RTK command rewriting

[ogallotti]

Summary

Add a Python plugin for Hermes (AI coding agent by Nous Research) that transparently rewrites terminal commands to RTK equivalents via the pre_tool_call lifecycle hook, achieving 60-90% LLM token savings.

This follows the same pattern as the OpenClaw plugin (#358).

Plugin structure

hermes/
├── __init__.py              # Thin delegate to `rtk rewrite` (~75 lines)
├── plugin.yaml              # Manifest declaring pre_tool_call hook
├── README.md                # Installation, architecture, usage docs
└── test_rtk_plugin.py       # 26 tests (binary detection, rewrite, hooks, edge cases)

How it works

Hermes has a Python plugin system with lifecycle hooks. Plugins live in ~/.hermes/plugins/<name>/ and contain a plugin.yaml manifest + __init__.py with a register(ctx) function.

This plugin:

1. Checks if rtk is in $PATH (cached, checked once)
2. Registers a pre_tool_call hook
3. On each terminal tool call, delegates to rtk rewrite <command>
4. Mutates args["command"] in-place if a rewrite is available

# Core flow (simplified)
def _pre_tool_call(*, tool_name, args, task_id, **_kwargs):
    if tool_name != "terminal":
        return
    command = args.get("command")
    rewritten = subprocess.run(["rtk", "rewrite", command], ...).stdout.strip()
    if rewritten and rewritten != command:
        args["command"] = rewritten

Design principles

• Thin delegate: all rewrite logic in rtk rewrite (Rust registry)
• Graceful degradation: never blocks command execution
• In-place mutation: Hermes passes a mutable dict, no return value needed
• 2-second timeout on rtk rewrite subprocess
• Zero dependencies: uses only Python stdlib (subprocess, shutil, logging)

Installation

mkdir -p ~/.hermes/plugins/rtk-rewrite
cp hermes/__init__.py hermes/plugin.yaml ~/.hermes/plugins/rtk-rewrite/

Tests

26 tests covering: binary detection, rewrite logic, hook behavior, edge cases (timeouts, crashes, non-terminal tools), and full integration flow.

$ python -m pytest hermes/test_rtk_plugin.py -v
26 passed in 0.03s

Changes to existing files

• hooks/README.md: Added Hermes to supported agents table, directory listing, integration tiers, and JSON format docs

Checklist

• Plugin follows thin-delegate pattern (same as openclaw/)
• Graceful degradation (exit 0 on all error paths)
• Tests pass (26/26)
• README with installation instructions
• hooks/README.md updated
• Compatible with Python 3.9+

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