Limits::max_alloc budgets the decoded pixel buffer, but the PNM decoder
collected one u32 per sample first (4x an 8-bit image, plus a u16 copy
for 16-bit) and PFM built a Vec<f32> beside the output bytes. Samples are
now rescaled and written straight into the native-endian output buffer
(reserved fallibly), so the only header-sized allocation is the one
Limits::check already charged.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
