Summary

Migrate the Go implementation from github.com/github/copilot-sdk/go v0.1.32 to v0.3.0.

Why

go list -m -u shows v0.3.0 is available. The upgrade is not just a dependency bump because the SDK session event API changed from a shared Data struct to typed per-event payloads.

Scope

• Update go.mod and go.sum to Copilot SDK v0.3.0.
• Migrate session event handling, transcript serialization, logging, web API mapping, usage collection, and tests to typed SDK event payloads.
• Update MCP server config conversion for the SDK's typed MCPServerConfig implementations.
• Keep existing transcript/result behavior compatible where possible.

Closed by #255.