Fix raw denoise on LINEAR-class images (sRaw, ProRAW)

[andriiryzhkov]

Raw denoise didn't work on Apple ProRAW and other pre-demosaiced LINEAR DNGs (reported on pixls.us: neural restore does not work with certain raw images). Preview rejected them outright; the patching path had a latent crash from an under-counted pixel_sz.

What it does

• Preview accepts the LINEAR class and routes through the linear pipeline
• pixel_sz multiplies by channel count - fixes the heap corruption that hit any multi-channel mipmap
• LINEAR write path: float mipmaps get cam values directly (already in [0, 1]); uint16 uses scalar un-prepare math
• Classifier drives the LINEAR/X-Trans split inside the patching function so 4BAYER (CYGM, RGBE) doesn't fall into FCxtrans with an unset xtrans pattern
• Warning toast on LINEAR images, deduped (once per imgid in preview, once per job in batch):

  raw denoise: this image is already pre-demosaiced (sRaw / computational raw); results may be limited

[TurboGit]

Thanks!