Add scvd.store to Websites

[cv-scvd]

What

Adds scvd.store to the Websites section: a live x402 general store for AI agents that also ships a parallel WebMCP surface.

Why it fits

The site registers four read-only tools via navigator.modelContext:

• read_store_guide — the store's own machine-readable guide/menu
• preflight_endpoint — free pre-payment simulation of any x402 endpoint's accepts selection logic (what a configured x402 client would sign, before any signature exists)
• check_conformance — free x402 v2 conformance checking against any issuer's signed offers/receipts, including competitors'
• verify_artifact — independent verification of a signed certificate against the store's published key

WebMCP tools here are deliberately read-only by design (nothing that moves money registers on navigator.modelContext); the store's own x402 payment flow is the separate, funded path. This is a live production site, not a demo — the tools back the same free conformance/preflight desk the store already runs at /api/conformance and /api/before-you-pay/v1.

Checklist

• Live, working site (not a demo/prototype)
• Actual WebMCP tools registered (not a stub)
• One entry, one PR
• Format matches existing README convention