The vertex shader stores depth as z / 65536, so reading it back with 65535
came out one too low whenever z's fraction was below z / 65536. Both the CPU
conversion and the shader path (used on GLES and at higher render
resolutions) had it. The shader also ran at the fragment shader's default
lowp, which mobile GPUs honor; 24 bits of depth need highp, sampler included
on GLES.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
