ImageCapture API：拍照与摄像参数控制

概述ImageCapture 允许对 `MediaStreamTrack` 执行拍照与参数控制（如变焦与闪光灯）。需从摄像头视频轨创建 `ImageCapture` 实例并检查能力。用法/示例const stream = await navigator.mediaDevices.getUserMedia({ video: { facingMode: 'environment' } }) const track = stream.getVideoTracks()[0] const ic = new ImageCapture(track) const photo = await ic.takePhoto({ imageHeight: 1080 }) const url = URL.createObjectURL(photo) // 能力探测与参数设置 const caps = await ic.getPhotoCapabilities() if (caps.torch) await ic.setOptions({ torch: true }) if (caps.zoom && caps.zoom.min < 2 && caps.zoom.max >= 2) await ic.setOptions({ zoom: 2 }) 工程建议检查能力并提供 UI 控件；在不支持环境回退到 `<video>` + `drawImage` 生成帧。管理 Blob URL 生命周期与释放，避免内存泄漏。处理权限与设备切换，记录失败原因与用户提示。参考与验证MDN：ImageCapture — https://developer.mozilla.org/docs/Web/API/ImageCaptureweb.dev：Image Capture — https://web.dev/articles/image-capture