feat(online): add OrcaRouter chat provider

[XiaoHuo888-hue]

📌 PR 内容 / PR Description

Add a named OrcaRouter online chat provider to LazyLLM's OnlineChatModule.

OrcaRouter is a unified multi-model gateway that exposes an OpenAI-compatible API (https://api.orcarouter.ai/v1/). This PR mirrors the existing DeepSeek/PPIO OpenAI-compatible gateway wiring so users can select it by name (source='orcarouter') instead of manually filling in a generic OpenAI-compatible endpoint. It also runs gateway-level, zero-trust security for AI agents on the same endpoint — screening every prompt/response and governing every tool call on a default-deny basis, with no application code changes.

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🎯 问题背景 / Problem Context

• LazyLLM already ships named providers (openai, deepseek, ppio, glm, kimi, qwen, ...). OrcaRouter is another OpenAI-compatible gateway, so adding a named provider keeps the user experience consistent and lets users route through OrcaRouter's smart-routing models (orcarouter/auto, orcarouter/fusion, orcarouter/fusion-flash, orcarouter/fusion-mini).

🔍 相关 Issue / Related Issue

• None (small provider addition following the existing supplier pattern in lazyllm/module/llms/onlinemodule/supplier/).

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✅ 变更类型 / Type of Change

• New feature

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🧪 如何测试 / How Has This Been Tested?

1. python3 -m flake8 on all changed files — clean.
2. pytest tests/basic_tests/Models/test_orcarouter_provider.py tests/basic_tests/Modules/test_map_model.py — 5 passed.
3. pytest tests/basic_tests/Models/test_online_chat_model_runtime.py — 59 passed (regression).
4. pytest tests/doc_check/test_doc_api_check.py -k OrcaRouterChat — passed (docs registration).
5. Live end-to-end (real API key): OnlineChatModule(source='orcarouter', model='orcarouter/auto') → https://api.orcarouter.ai/v1/chat/completions → HTTP 200 ORCA-LIVE-OK. All four gateway models (orcarouter/auto, fusion, fusion-flash, fusion-mini) returned ORCA-LIVE-OK.

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⚡ 更新后的用法示例 / Usage After Update

import lazyllm
# export LAZYLLM_ORCAROUTER_API_KEY=sk-orca-...
chat = lazyllm.OnlineChatModule(source='orcarouter', model='orcarouter/auto')
print(chat('Hello!'))

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⚠️ 注意事项 / Additional Notes

• Default base_url is https://api.orcarouter.ai/v1/ (trailing slash, matching the existing openai.py convention so urljoin produces /v1/chat/completions).
• OrcaRouter is a chat-only gateway — no embedding/rerank endpoints were added.

🧠 AI 参与情况 / AI Involvement

• 使用 AI 辅助（局部代码）/ AI-assisted (partial code)

使用工具 / Tools Used：

• ClaudeCode