feat: enable multi-mode protocol testing for both TCKs

[kabir]

Add CI for 0.3 TCK, and multi-mode testing (v1.0 + v0.3 together) for both TCK servers.

• Add Legacy_0_3_AgentInterface and additionalInterfaces to AgentCard so v1.0 cards are parsable by v0.3 clients
• Add DerivedAgentCardProducer in compat-0.3/tck to convert v0.3 AgentCard to v1.0 format for multi-mode
• Add multiversion dispatcher deps to both TCK multi-mode profiles
• Fix global BodyHandler consuming gRPC request bodies by moving to per-route BodyHandler in A2AServerRoutes
• Ignore additionalInterfaces in gRPC AgentCardMapper
• Add Compat03Fields utility to selectively add v0.3 fields to v1.0 AgentCard producers when running in a multi-version setup
• Enable previously @disabled multiversion agent card tests
• Allow Long JSON-RPC request ids

[gemini-code-assist]

Code Review

This pull request implements backward compatibility for v0.3 clients by enhancing the v1.0 AgentCard model with legacy fields (url, preferredTransport, and additionalInterfaces) and providing a mechanism to populate them when both protocol versions are enabled. It includes significant updates to documentation, TCK profiles, and test suites to support multi-version environments. Furthermore, it refines the server's request handling by moving the BodyHandler to a per-route basis to avoid conflicts with gRPC services. I have no further feedback to provide as the existing review comment was purely explanatory.

[kabir]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces backward compatibility for v0.3 clients by adding legacy fields to the v1.0 AgentCard and providing utilities to populate them. It also refines JSON-RPC ID validation to include all Number types and moves Vert.x BodyHandlers to a per-route basis to avoid gRPC conflicts. Feedback highlighted a potential NullPointerException in the DerivedAgentCardProducer when additionalInterfaces is null and suggested including the primary v0.3 endpoint in the interface mapping.