Performance issue with > 4096-pixel images in Vello Classic

Hi :) I'm having a performance issue with Vello Classic. I'm filling a full-screen rectangle with a 1835 by 8192 image on an iPad Pro 2025 13", and I'm unable to sustain 120 FPS. I'm not doing anything else with the GPU. If I scale the image down (proportionally) to a height of 4096, the frame rate recovers to 120 (the display's refresh rate). However if I scale it to 4097, the problem persists, suggesting some kind of threshold at 4096 pixels. What could be going wrong here? Two other less significant issues: - `ImageQuality::High` does not yield bicubic filtering. - Image sizes of more than 8192 silently fail to render. I'd expect an error somewhere. Tested with revision Vello commit `ea2a935d4c502c` and `--release`.