Function execute_tool_batch 

pub async fn execute_tool_batch(
    state: &AppState,
    calls: &[PendingToolCall],
    ctx: &mut ToolBatchContext,
    metrics: &mut ToolMetrics,
    event_tx: Option<&UnboundedSender<AgentEvent>>,
    chat_id: i64,
    iteration: usize,
    caller_channel: &str,
    explicit_user_approval: bool,
    trace_id: &[u8],
    parent_span_id: &[u8],
) -> Vec<ContentBlock>

Execute a batch of tool calls, optionally in parallel.

When parallel_enabled is false, all tools execute sequentially (existing behavior). When true, tools are partitioned into waves and ReadOnly tools within a wave run concurrently.