Docs - Clean up Checkout use case page

[MantisClone]

Problem

Checkout use case page contains AI warning, marketing fluff, placeholder links, speculative content, and "coming soon" notices that undermine credibility and user experience.

Key issues:

• AI-generated warning box at top
• Claims "80+ wallets" - needs verification against actual integration
• Multiple "coming soon" placeholders (interactive quickstart, embed code, fork guide)
• Claims "80+ tokens" conflicts with Payment Detection page's "150+ currencies"
• Placeholder # links in cards
• Code examples show non-existent @requestnetwork/payment-widget package
• No tooltips for technical terms (crosschain, QR code, blockchain, etc.)
• Section structure needs cleanup (too many tabs/accordions)

Proposed Solution

Apply Invoicing/Payment Detection cleanup template to Checkout page:

• Remove AI warning box
• Verify wallet support claim (likely referencing WalletConnect's 80+ wallets)
• Update currency/token counts to match Payment Detection (150+ currencies)
• Remove or clearly mark all "coming soon" content
• Fix placeholder links or add notes for future pages
• Replace code examples with accurate implementations (payment-widget doesn't exist as npm package)
• Add tooltips for technical terms (wallet, crosschain, QR code, blockchain, escrow, etc.)
• Simplify section structure (reduce tabs/accordions where possible)
• Verify EasyInvoice demo link accuracy
• Replace marketing language with factual, benefits-focused copy

Considerations

• Checkout is a key use case - needs to be accurate about what's actually available
• Payment widget exists in web-components monorepo, not as standalone package
• "Coming soon" content should either be removed or moved to separate tracking issue
• EasyInvoice demo at https://easy-invoice-demo.vercel.app/pay should be verified
• Integration patterns should reflect actual implementation options (web-components, API direct)
• Customer experience benefits should be factual, not speculative
• Code examples should use actual Request Network packages and patterns

References

• Parent issue: Docs - Remove AI slop from Use Case pages #18
• Template issues: Docs - Clean up Invoicing use case page #28 (Invoicing), Docs - Clean up Payment Detection use case page #29 (Payment Detection)
• Current page: /use-cases/checkout.mdx
• Web Components repo: https://github.com/RequestNetwork/web-components
• EasyInvoice demo: https://easy-invoice-demo.vercel.app/pay