Add site share links

[dragonforce2010]

Summary:

• Add a small share row to the final site CTA for X, Hacker News, and Reddit.
• Keep primary conversion actions focused on local run, repo, and CLI package.

Verification:

• bun install --frozen-lockfile
• git diff --check
• bun run test:public-hygiene
• bun run typecheck
• bun run lint
• bun run build

Visual proof:

• /tmp/openmaple-site-share-links-desktop-20260620.png
• /tmp/openmaple-site-share-links-mobile-20260620.png