Function run_agent 

pub async fn run_agent(
    provider: &dyn ModelProvider,
    tools: &[Arc<dyn Tool>],
    messages: &mut Vec<AgentMessage>,
    model: &Model,
    config: &RunConfig,
    cancel: &CancellationToken,
    hooks: &RunHooks<'_>,
) -> Result<RunOutcome>

Run the agent loop.

messages is seeded by the caller (typically a System message followed by a User message) and mutated in place as the loop appends assistant turns and tool results.

Budgets (from RunConfig):

• max_turns caps total model turns.
• turn_timeout_ms caps each provider invoke.
• max_tool_calls_per_turn rejects runaway responses.

Concurrency: when tool_concurrency > 1, tool calls within a turn run on a JoinSet with the configured cap; results are always appended in the order the model issued them. tool_concurrency == 1 is sequential.

Cancellation: the loop checks cancel.is_cancelled() between turns and composes it into each tool call.