feat(models,landing): add OpenRouter free models and a free-models article (#60)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/docs/content/models.en.md

@@ -73,6 +73,8 @@ Built-in groups and their env-var fallbacks (catalog source: `packages/core/src/
 
 The gateway groups (openrouter / fireworks / siliconflow / qwen-token-plan / qwen-pay-as-you-go) go through AgentHub's OpenAI client, so with blank credentials they read `OPENAI_API_KEY` — not a gateway-specific variable.
 
+The preset catalog also carries OpenRouter's free tier: `:free` model variants (e.g. `inclusionai/ling-3.0-flash:free`, `poolside/laguna-m.1:free`) and the `openrouter/free` unified Free Models Router. They cost nothing, but are subject to OpenRouter's free-tier rate limits and data policy.
+
 Some models in the preset catalog: deepseek-v4-pro / deepseek-v4-flash, gemini-3.1-pro-preview, claude-opus-4-8 / claude-sonnet-4-6, gpt-5.5, glm-5.2, kimi-k2.6, qwen3.8-max-preview (not exhaustive).
 
 ## Thinking levels

packages/docs/content/models.zh.md

@@ -73,6 +73,8 @@ api_key = "sk-..."
 
 网关分组(openrouter / fireworks / siliconflow / qwen-token-plan / qwen-pay-as-you-go)经 AgentHub 的 OpenAI 客户端请求，因此凭证留空时读取的是 `OPENAI_API_KEY`，而非网关自己的变量名。
 
+预置目录还收录了 OpenRouter 的免费档：`:free` 模型变体(如 `inclusionai/ling-3.0-flash:free`、`poolside/laguna-m.1:free`)与统一路由 `openrouter/free`(Free Models Router)，零成本可用，但受 OpenRouter 免费档速率限制与数据政策约束。
+
 预置目录中的部分模型：deepseek-v4-pro / deepseek-v4-flash、gemini-3.1-pro-preview、claude-opus-4-8 / claude-sonnet-4-6、gpt-5.5、glm-5.2、kimi-k2.6、qwen3.8-max-preview 等(非完整清单)。
 
 ## 思考等级