Flatten model-divergence subtasks into 3 independent tasks

Replaced parent+subtask structure with 3 standalone tasks:
- mde-manifest-detection (foundational: models.json schema, detect_models.py)
- mde-interactive-enforcement (conflict matrix, --model args, audit, badges)
- mde-loop-enforcement (loop.json per-role model, {model} substitution, check-gate)

Parent archived to tasks/complete/ for history. Each task has its own
SPEC.md and is at research:awaiting_approval.

Rationale: subtasks are independently actionable with their own lifecycle.
Parent container added complexity without benefit.

tasks/mde-manifest-detection/.state

@@ -0,0 +1 @@
+research:awaiting_approval