Add Bazaar marketplace discovery support

[mmurrs]

Summary

This PR adds Bazaar / Agentic Market discovery support to dual402, so paid routes can be surfaced through x402 discovery and indexed after CDP settlement.

What’s Included

• Publishes Bazaar-ready metadata from GET /.well-known/x402, including the route resource, payment requirements, and extensions.bazaar.
• Adds route-level Bazaar examples via bazaar.inputExample, bazaar.outputExample, and bazaar.bodyType, so marketplace listings can show realistic request/response shapes.
• Sends server-owned paymentPayload.resource and Bazaar extensions through CDP /verify and /settle, which is the path Bazaar uses for cataloging.
• Keeps this opt-in and safe: plain dual.charge() routes do not advertise Bazaar metadata, and client-injected Bazaar metadata is stripped.
• Adds tests for discovery output, POST route metadata, CDP payload shape, hostile metadata stripping, and the full unpaid-to-paid flow.

Validation

• npm run check passes with 16 tests.
• git diff --check passes.