Typed structs for Raxol.Agent.Stream events plus conversion helpers.

Stream.run/2 and Stream.react/2 emit events as bare tuples for pattern-match ergonomics and backward compatibility:

{:text_delta, "hello"}
{:tool_use, %{name: "linear_graphql", arguments: %{}, id: "call_1"}}
{:tool_result, %{name: "linear_graphql", result: %{...}}}
{:turn_complete, %{content: "...", usage: %{}, iteration: 1}}
{:done, %{content: "...", tool_results: [...], usage: %{}}}
{:error, reason}

Consumers that want stronger typing -- e.g., orchestrators forwarding events to surfaces -- can use from_tuple/1 to lift each tuple into a typed struct, and to_payload/1 to project it down to a generic map suitable for telemetry or pubsub.

Both helpers are pure; they do not subscribe to or transform the underlying stream.

Example

stream = Raxol.Agent.Stream.run(prompt, opts)

Enum.each(stream, fn event ->
  typed = Raxol.Agent.Stream.Event.from_tuple(event)
  send(parent, {:run_event, key, Raxol.Agent.Stream.Event.to_payload(typed)})
end)

See Raxol.Agent.EventForwarder for the common "send to parent" pattern packaged as a single call.