Responsive requirements

Founder Profiles is highly photo-driven — the 1:1 avatar dominates the visual hierarchy. Mobile collapses the snapshot sidecard below the hero, keeps the avatar prominent, and stacks the linked-startup block + Related Signals + social links vertically.

Per-breakpoint behaviors

Mobile (≤640px)

Listing: 1-up grid. Avatar prominent (96px). Detail: hero stacks vertically (avatar → identity row → snapshot → about → linked startup → signals). Filter row becomes horizontal scroll.

Tablet (641-1023px)

Listing 2-up. Detail: 2-column hero (main + snapshot). Linked startup full-width.

Desktop (≥1024px)

Listing 3-up. Detail: full layout with snapshot sidecard sticky on long scrolls (Phase 2).

Photo-specific rules

• Avatar is 1:1 with `object-fit: cover` and `border-2 border-border` (or `border-accent` when elevated).
• Initial-circle fallback when no photo URL: 2-letter initials with subtle gradient background.
• Photo dimensions scale: card avatar 44px → listing card 96px → detail hero 144px.
• Editorial discipline: no AI-generated portraits. Real photos only.