Migrate from A2A v0 to v1 (part 1)

[supreme-gg-gg]

The 1st of 3 PRs for A2A v0 to v1 zero downtime migration. This will go into release 0.10.0

Makes the controller compatible with A2A v0 (trpc-a2a-go) and v1 (a2a-go) data and both v0 and v1 JSON-RPC routes / agent card routes depending on A2A-Version header (designed explicitly by the protocol for version negotiations). Replaces all internal usages of trpc-a2a-go with a2a-go except in data conversion code and CLI client code.

This ensure that the controller is compatible with old / existing agents and UI in A2A v0 and existing v0 data in db, while adding the capability to communicate with v1 agents and UI during upgrade as they are added in the next part.

Follows https://a2a-protocol.org/latest/whats-new-v1/#migration-strategy-recommendations and db conversion reuses as much of existing a2a backward compatible code as possible.

[chromatic-com]

Warning

Testing paused

Monthly snapshot limit reached. Update your plan to get more snapshots and resume testing.

[supreme-gg-gg]

For reviewer, tracing context injection and associated tests have been moved to client_interceptors.go and client_interceptor_test.go (also where auth headers injection happens)

[supreme-gg-gg]

For reviewer, this is a modified version of existing https://github.com/kagent-dev/kagent/blob/main/go/core/internal/a2a/manager.go (removed) for very similar functionality

This new passthrough handler is simpler and forwards RPC methods directly to the client and avoids having to go through things like task lifecycle, task status, etc. that the old AgentExecutor would do, and fits better since the controller is just a proxy to upstream agent runtime that handles the real executor.

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[supreme-gg-gg]

@copilot review