[feat] opencode 加上modalities支持

[fcying]

不配置这个. opencode 无法识别图片

https://opencode.ai/config.json
              "modalities": {
                "type": "object",
                "properties": {
                  "input": {
                    "type": "array",
                    "items": {
                      "type": "string",
                      "enum": [
                        "text",
                        "audio",
                        "image",
                        "video",
                        "pdf"
                      ]
                    }
                  },
                  "output": {
                    "type": "array",
                    "items": {
                      "type": "string",
                      "enum": [
                        "text",
                        "audio",
                        "image",
                        "video",
                        "pdf"
                      ]
                    }
                  }
                },
                "additionalProperties": false
              },

[SaladDay]

Thanks @fcying. This is not in 5.8.1, but the request is clear: OpenCode provider config needs a modalities editor/preserved field so image-capable providers can advertise input = ["text", "image"] and related values.

Keeping this open for a follow-up release.