Design headless mode contract for mgw CLI

[snipcodeit]

Description

Define --headless flag contract: which commands support it, how they handle prompts (default to safe action), what JSON output format they emit for CI consumers. Write spec in docs/HEADLESS.md.

Acceptance Criteria

• Design headless mode contract for mgw CLI

GSD Route

plan-phase

Phase Context

Phase 30: Headless Mode and GitHub Actions Integration of v4 — Standalone and CI Usage

Depends on

none