Android hardware VP9 accepts spatial SVC, then drops the layers

Hardware VP9 encoders on Android accept L3T3 (three spatial and three temporal layers) but return a single flat stream without the lower spatial layers. The behavior appears on Samsung and Pixel devices with Qualcomm and Tensor chips; software libvpx produces real spatial layers at the cost of CPU and battery.

• L3T3 is accepted, but the bitstream keeps only the top-resolution layer
• The issue appears on Samsung and Pixel with Qualcomm and Tensor
• libvpx emits real spatial layers but costs CPU and battery
• getSupportedLayeringSchemas() on Android 17 reports only temporal l1tN