test(x402): prove Bazaar extension reaches both facilitator legs

[AgentTanuki]

Summary

• capture the server-declared extensions.bazaar after validation at the fake facilitator's /verify and /settle legs
• assert the official x402 client preserves the exact Bazaar declaration from the unpaid 402 through both facilitator calls
• keep production behavior, pricing, rails, service version, and generated artifacts unchanged

Validation

• pytest live/guild/tests_x402_interop -q — 4 passed
• git diff --check
• independent hostile review: ready, with no blocking correctness or race finding under the repository's serial interop CI path

Scope

Test-only: two files under live/guild/tests_x402_interop/. The assertion treats the Bazaar extension as deterministic per resource, which is true for the current contract. This fake-facilitator test proves buyer echo and both facilitator legs; it does not claim that hosted CDP has indexed Agent Guild before the first independent paid settlement.