chore(main): release 5.0.0

[github-actions]

🤖 I have created a release beep boop

5.0.0 (2026-05-10)

⚠ BREAKING CHANGES

• types: callers passing affected_packages into a function typed def f(x: list[Package]) will see a mypy error and need to migrate to Sequence[Package]. Runtime behavior is unchanged; the change is annotation-only.
• types: Subclasses that add fields without Field(exclude=True) will now have those fields appear in model_dump() output where they were previously dropped by Pydantic's declared-schema firewall. Audit each subclass and mark internal fields with Field(exclude=True). To restore the prior behavior at a specific call site, pass serialize_as_any=False explicitly.
• webhooks: domain kwarg removed from create_mcp_webhook_payload and WebhookSender.send_mcp. Migrate to protocol (kebab-case string or AdcpProtocol enum value).
• webhooks: create_mcp_webhook_payload returns a Pydantic model, not a dict; task_type is now required.

Features

• a2a: add public_url param to agent card for production deployments (#621) (14d294c)
• server: add TenantRegistry with per-tenant health tracking (#628) (ae687b6)
• server: default MCP streamable-http to stateful with idle eviction (#636) (3173a54)
• server: expose RequestContext.transport and current_transport ContextVar (#627) (20e5d53)
• server: pre-validation request hook for spec-default injection (#614) (#629) (05d4cd8)
• testing: adopter type-checking test suite with zero-ignore contract (#634) (20e496c)
• testing: extend build_asgi_app with full serve-layer kwargs (#626) (8679a95)
• types: default serialize_as_any=True in AdCPBaseModel.model_dump (#639) (3160ace), closes #615
• types: widen extension-point list[X] to Sequence[X] (#624) (#640) (96ccfd4)
• webhooks: create_mcp_webhook_payload returns McpWebhookPayload (#632) (9eb962c)
• webhooks: replace domain kwarg with typed protocol (AdcpProtocol enum) (#637) (fdd4053)

Bug Fixes

• server: register /.well-known/agent.json alias route in create_a2a_server (#613) (2989101)
• server: strip None-valued asset fields from dict-based response builder output (#631) (c02ea84), closes #622
• types: widen canceled Literal[True]=True to Literal[True]|None=None on request types (#643) (120ae3b)

Documentation

• types: document Field(exclude=True) and @model_serializer for nested wire isolation (#630) (4912af9)

---

This PR was generated with Release Please. See documentation.

[github-actions]

🤖 Created releases:

• v5.0.0

🌻