hermes - 💡(How to fix) Fix feat: add Volcengine (火山引擎) as built-in provider

Feature Description

Add Volcengine (火山引擎 / ByteDance) as a built-in model provider in Hermes Agent, supporting their Coding Plan (Agent Plan) subscription.

Motivation

Volcengine already has an official Hermes Agent integration guide in their documentation:

• https://www.volcengine.com/docs/82379/2373743 (Agent Plan → Hermes Agent)

They support the same DeepSeek models (V3, R1, V4) through an OpenAI-compatible API at a subscription-based pricing model that is significantly more cost-effective than per-token pricing.

Why this matters for Hermes users:

• Volcengine Coding Plan offers fixed monthly pricing with generous token quotas
• Same model quality (DeepSeek-V4, etc.) at a fraction of per-token cost
• Many Chinese developers already use Volcengine for AI services
• They already have integration docs for Claude Code, OpenCode, OpenClaw, Hermes Agent, TRAE, OpenViking — showing clear intent to support the AI coding agent ecosystem

Technical Details

API endpoint: https://ark.cn-beijing.volces.com/api/v3 Auth: API Key (Bearer token) Format: OpenAI-compatible Chat Completions API Models available through Coding Plan: DeepSeek-V3, DeepSeek-R1, DeepSeek-V4, Doubao, etc.

Configuration reference (from their Hermes Agent doc):

model:
  provider: volcengine
  base_url: https://ark.cn-beijing.volces.com/api/v3
  api_key: <your-api-key>
  default: deepseek-v4

Proposed Solution

Add volcengine as a provider preset in Hermes Agent, similar to how DeepSeek, OpenAI, Anthropic etc. are already built-in. The preset should:

1. Pre-configure base_url to https://ark.cn-beijing.volces.com/api/v3
2. Show up in hermes model interactive picker
3. Support API key via VOLCENGINE_API_KEY env var
4. List available models (deepseek-v3, deepseek-r1, deepseek-v4, etc.)