Ad creative variations for split-testing with a fixed product hero

I have a single product hero image and I want to generate 8 background / scene variations around it so I can split-test ad creative without re-shooting. img2img + inpainting will keep the product itself untouched while changing everything around it.

Product hero image filename: {{hero_filename}}
What the product is: {{product_description}}
Audience I'm testing against: {{audience}}
Hooks I'm testing (one per variation): {{hooks}}
Channels these will run on: {{channels}}
Brand boundaries I must stay inside: {{brand_boundaries}}

Give me a Stable Diffusion img2img + inpainting workflow:

1. PREP - how to mask the product in the hero image so only the background changes. (Inpaint > mask the product > invert mask > inpaint only the unmasked area.)

2. EIGHT BACKGROUND PROMPTS - one per hook in {{hooks}}. Each is a comma-separated SD prompt for the BACKGROUND only. Format:
   - Hook: [the hook]
   - Scene prompt: [SD tokens]
   - Mood tokens: [lighting + colour]
   - Why it matches the hook: [one line]

3. SHARED NEGATIVE PROMPT - kills off-brand elements, hands, text, watermarks, low quality, busy clutter. Pull from {{brand_boundaries}}.

4. img2img DENOISING STRENGTH - the right range so the background changes meaningfully but the product edges stay clean. Tell me what to adjust if the product itself starts morphing.

5. POST-GEN CHECK - three things to eyeball on each output before pushing to ads: edge halo around the product, colour cast from the new background, shadow direction matching the product's original lighting.

AU English. Format so I can paste each background prompt straight into Automatic1111 inpaint mode.