Tuttotorna/Pre-Deployment-Structural-Gate: v0.0.1 — Stable Structural Gate API

Initial stable release of the Pre-Deployment Structural Gate (PDSG). This release establishes a frozen public API for a post-hoc, model-agnostic structural gate designed to detect saturation, irreversibility, and instability before scaling or deployment. PDSG provides categorical verdicts (GO / NO_GO / RISK / UNSTABLE) and a confidence envelope (ICE), without accessing model internals or exposing structural metrics. The gate is engine-agnostic and ready to consume private structural engines (e.g. OMNIA) via a strict adapter contract, while remaining fully functional as a standalone defensive pre-check.