docs: clarify Bazaar v2 metadata placement

[Bortlesboat]

Summary

This tightens the Bazaar v2 docs/spec around where seller-declared metadata actually lives.

• update Bazaar docs and the seller quickstart to show v2 metadata in resource plus extensions.bazaar
• remove or reframe examples that implied sellers should put Bazaar metadata directly in accepts[]
• align the MCP examples in the Bazaar spec with the live toolName field used by the SDKs

Why

Issue #1945 points at a real source of confusion: the repo currently mixed v1-style enriched accepts[] examples with the v2 wire contract. That makes it hard to tell which fields are seller-declared versus facilitator-enriched catalog output.

This PR is docs/spec only. It does not change facilitator behavior or the public catalog shape.

Refs #1945

Verification

• npx --yes prettier --check docs/extensions/bazaar.mdx docs/getting-started/quickstart-for-sellers.mdx specs/extensions/bazaar.md
• git diff --check

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