v0.3.0

Added

• Consults (Rho.Consult): run(model, prompt, opts) asks another
  model (a google: Gemini model while Claude leads, say) and returns
  {:ok, %{text, model, purpose, usage}}, or {:error, reason}
  ({:signed_out, provider} without a credential, :stopped,
  {:cost_cap, spent, cap}, the model call's error; describe/1 words
  it). Options: :purpose ("critique", "second_opinion" or free
  text), :system, :attachments (by ref or path), :tools the
  consulted model may call (with :max_iterations), :max_tokens,
  :llm, :budget. With :loop the consult is the session's:
  consult_start / consult_delta / consult_end events to the loop's
  subscribers, its usage recorded as a custom "<ns>.consult" entry
  (Rho.Session.consult/1, counted by Rho.Session.totals/1) and
  against the loop's daily cost cap, stopped by Rho.Loop.stop/1 (even
  when the loop is idle) or the loop exiting, and :include_conversation
  sends the conversation so far as a transcript (the calls in flight left
  out, the newest part when it's too long). The model call runs in a
  worker that dies with its caller.
• ask_model (Rho.Tools.Consult, not a built-in): the lead model
  consults another (model, purpose, prompt, include_conversation)
  and gets "<model> (<purpose>):" and its answer back, with %{model, purpose, usage} as the result's details.
• Attributed messages: Rho.Loop.prompt/3, steer/3 and
  follow_up/3 take options as their third argument (:attachments,
  :attribution, :instruction); attribution: {:model, model, purpose} stores the text as that model's message, a custom_message
"<ns>.model_message" (Rho.Session.model_message/4, read back with
  Rho.Session.attribution/1), sent to the lead marked as that model's,
  not the user's, followed by the :instruction.
• config :rho, :consult_models (the models that may be consulted; default
  every catalog model of a signed-in provider; Rho.Consult.models/0,
  allowed/1) and :consult_system (a consulted model's system prompt
  per purpose).
• Rho.Loop.snapshot/1 lists the consults running (consults).