Define human-approval-gate standard for irreversible actions, incl. chained/multi-agent flows

## Description

Define where and how a mandatory human-in-the-loop checkpoint must sit before an agent — or any agent within a multi-agent chain — executes an irreversible or high-consequence action.

## Source

Krav 4 "Godkjenningspunkt før handlinger med vesentlig konsekvens" and Krav 12 "Godkjenningspunkter i kjeder": a checkpoint at the system's entry point is not sufficient — it must sit immediately before the consequential action, regardless of which agent in the chain performs it.

## Business Goal

This is the control that keeps a human accountable for irreversible outcomes. Without it, Class 3 agents and multi-agent systems can act autonomously in ways nobody explicitly approved.

## Acceptance Criteria

- A documented pattern for placing approval checkpoints exists, covering both single-agent and orchestrator/sub-agent architectures.
- Guidance requires checkpoint placement to be justified per-action in a system's documentation, not assumed from a single entry-point check.
- The pattern is referenced from the classification scheme: Class 3 requires at least one such checkpoint.

## Dependencies

Depends on the classification-scheme issue in this epic. Coordinates with the mandate-delegation-limits issue for multi-agent systems.