Fix mobile landing automation mockup layout

[SawyerHood]

Summary

• keep the landing page automation phone mock out of the hero mock mobile bleed/zoom rules
• preserve the top hero mock's intentional mobile off-screen bleed
• avoid horizontal page scroll on iPhone-width layouts

Validation

• pnpm exec turbo run build --filter=@bb/landing
• pnpm exec turbo run typecheck --filter=@bb/landing
• browser QA at 390px wide: automation mock fit within the content column and document scroll width stayed at viewport width