feat(protocol): support AdCP 3.2.0 beta.3

[bokelley]

Summary

• pin and vendor the signed AdCP 3.2.0-beta.3 schema bundle, regenerate the versioned/runtime type surfaces, and publish the new placement presentation and preview renderer models
• preserve beta.3 protocol behavior across selector validation, MCP discovery, catalog-only adagents.json, preview capabilities, signing vectors, and CONFLICTING_SELECTORS
• harden delegated previews and reference renderers with isolated rendering guidance, bounded expiry-aware caching, HTTPS/origin validation, full renderer validation, and trusted community-registry ingestion
• repair batch preview dispatch and separate URL/HTML cache identities
• document the beta.3 migration and generated model delta

Provenance

• upstream tag: v3.2.0-beta.3 (4776f972e55e49786f0da27b6a617c2989fd5358)
• verified bundle SHA-256: cb84583547e76981a0f50099ae4c3b815c9bb02a21aa501400bcd84b601805fb
• bundle contents: 1,391 schemas and 8 skills

Validation

• make ci-local
• clean full regeneration with 852 timestamp-only modules restored and 17 semantic generated modules retained
• wheel/sdist build, Twine metadata validation, isolated wheel import smoke, and beta.3 schema inventory checks
• code, protocol, and security expert reviews approved with no remaining blockers

Compatibility boundary

Product-aware equivalence across co-present legacy and canonical selector routes remains seller application logic. Draft 7 JSON Schema cannot evaluate whether independently resolved selectors choose the same product-option set; adapters must reject disagreement with CONFLICTING_SELECTORS before applying precedence.

[bokelley]

All required CI checks are green. Ladon completed two independent analysis passes with zero findings; both runs failed only when launching the post-review arbiter (Argument list too long) after producing the clean structured findings. Local code, protocol, and security expert reviews also approved the final integration. Proceeding via the repository admin merge path because the non-required review transport cannot handle this 1,462-file vendored schema update.