Mission Run Overview
Mission Run: Mission-Type DRG Node + Cross-Grain Integrity Gate (S0 + seam completion)
Make mission_type a first-class DRG node and land cross-grain integrity as a doctrine-integrity gate on real content, wiring the live action-grain lazily and retiring _EMPTY_GRAIN - activation gating byte-identical.
Bundles #2651 (resolver-seam completion) with the first step of ADR S0. Per the ADR-anchored adjudication, cross-grain disjointness (FR-013) belongs in a doctrine-integrity/DRG consistency gate on real content, not a swallowed hot-resolver raise, and its home requires mission_type to be a first-class DRG node. So this mission makes mission_type a DRG node, enforces cross-grain integrity as a gate with a non-vacuity twin, wires the live action-grain lazily (retiring _EMPTY_GRAIN, overlay-aware root), reconciles the two test-side unions, and campsites the seam - keeping activation gating byte-identical. A precursor that de-risks S3.