feat(protocol): support AdCP 3.2 beta lifecycle

[bokelley]

Summary

• sync and generate the AdCP 3.2.0-beta.0 schema bundle and public types
• add the compact list, proposal, purchase, and media-buy control lifecycle across client, MCP, A2A, server, CLI, and decisioning surfaces
• add 3.0, 3.1, and 3.2 old/direct/proposal compatibility coverage
• enforce the 3.2 request-signing body-integrity profile while preserving negotiated legacy behavior
• document the 3.1 to 3.2 migration and package the complete 3.2 schema bundle

Compatibility fixes found during migration

• preserve prerelease wire-version normalization and canonical schema references
• accept legacy creative asset instances across generated aggregate unions
• retain legacy create/update media-buy status and update-rights response compatibility
• default 3.2 request-signing capability projection to required content-digest coverage

Validation

• 6,446 passed, 40 skipped, 9 deselected, 1 xfailed
• ruff, mypy, strict adopter fixtures, type-ignore contract, bandit, and pre-commit hooks pass
• clean type regeneration passes
• wheel and sdist build successfully; wheel contains all 1,386 AdCP 3.2 JSON schemas

[aao-secretariat]

MUST FIX: sync_agent_notification_configs (L364-365) and report_plan_adjustment (L442-443) are added as new @abstractmethods on ProtocolAdapter, a public export from adcp.protocols. Any external subclass now fails to instantiate — TypeError: Can't instantiate abstract class ... with abstract methods report_plan_adjustment, sync_agent_notification_configs. That is a breaking change to the public surface shipped under feat(protocol):; release-please cuts a minor, so the break lands without a major.

Note the inconsistency: every other new task in this PR — list_products (L177), buy_products (L193), the rest of the compact lifecycle — was deliberately added as a concrete method that raises NotImplementedError, precisely so existing subclasses keep working. These two are the only abstract additions. Either make them concrete-with-NotImplementedError to match (additive, non-breaking), or mark the commit feat! with a migration note.