Event struct passed to hooks during execution.

This provides a uniform interface for hooks across all node types, eliminating the need for workflow access during the execute phase.

Fields

• :timing - :before or :after indicating when the hook is running
• :node - The node struct being executed (Step, Condition, etc.)
• :node_hash - Hash of the node for quick identification
• :input_fact - The input fact triggering this execution
• :result - For after hooks: the result of execution (Fact, boolean, etc.)

Example

# New-style hook (arity-2, workflow-free)
fn %HookEvent{timing: :before, node: step}, ctx ->
  Logger.info("Executing step #{step.name}")
  :ok
end

# Hook returning an apply_fn for workflow modifications
fn %HookEvent{timing: :after, result: fact}, _ctx ->
  {:apply, fn workflow ->
    Workflow.add(workflow, some_step, to: fact)
  end}
end