[raiseCatError]

Replaces the outdated OpenDisplay-era social card in public/og.png ("Use your partner's iPad as your Mac's second monitor") with the current MeowDisplay preview, matching the website's new general og:image (raiseCatError/MeowDisplayWebsite#25).

Changes

• public/og.png: 1200 × 630 PNG (234 KB). "Mac everywhere. On whatever display." with genuine MeowDisplay screens: the Mac app Overview, an iPad in Window view and an iPhone with the Control Tray. Rendered by scripts/render_social_previews.py --og-png in the website repo.
• index.html: og:image:alt and twitter:image:alt now describe the new image. Type (image/png) and size (1200 × 630) are unchanged and still correct.
• README.md: shows public/og.png instead of a separate copy, and removes the duplicate assets/readme/website/social-preview-v3.jpg.

Not changed: app code, CI, and the rest of the legacy landing page. Its src/App.tsx still rotates "partner's iPad" in the hero copy; left for a separate decision.

Checks: pnpm install --frozen-lockfile && pnpm run build passes; prerendered docs/index.html carries the new alt text and docs/og.png is the new image.

[raiseCatError]

Closing as superseded by #136, which removes the legacy React/Vite landing page entirely, including public/og.png and index.html. Nothing here needs carrying over:

• The new og.png and its alt text only existed to keep the old page alive. The new general social preview lives on the canonical website (raiseCatError/MeowDisplayWebsite#25), and GitHub's repository preview never used public/og.png (it's the auto-generated card).
• The README change pointed the hero image at public/og.png, which no longer exists. README keeps its existing, valid assets/readme/website/social-preview-v3.jpg.
• This PR also targeted main, which per BRANCHING.md only changes through release promotion.

Branch site/og-meowdisplay-brand is left in place.