Adds SupersideBriaBackgroundReplaceNode (fal-ai/bria/background/replace) as
its own node - the richer generative background-replace model (reference
image, prompt refine, fast/quality toggle, multiple variations). The
existing SupersideBriaReplaceBackgroundNode stays exactly as it was,
pointing at bria/replace-background ("Replace Background V2").
README now documents all three Bria background nodes with a chooser table
and an explicit note: the two generative "Replace" nodes cannot produce an
exact flat hex color (they re-light and may alter the subject) - for an
exact catalogue-flat hex background use the Background Standardizer.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
