Remove legacy discovery fallback for 0.3.3

[kev1n]

Summary

• remove the temporary dual-reader discovery bridge now that the replacement server contract is deployed
• require nested USD pricing, ranked search relevance, and the dedicated /catalog/search operation
• publish the bundled discovery skill and CLI package as 0.3.3

Validation

• npm ci
• npm run build
• npm test (43/43)
• npm pack --dry-run
• git diff --check

Rollout

The compatibility release 0.3.2 is already published and the server/frontend contract cut is live. Merge this PR, then publish tag v0.3.3 as the cleanup release.