Mixed_CFM: absorb Unified_CFM primitives; remove Unified_CFM

Mixed_CFM was loading AdaLNBlock / SinusoidalTimeEmb / _sinkhorn_coupling
and flow-feature helpers from Unified_CFM via importlib spec hacks. Pulled
those symbols into Mixed_CFM/_layers.py (model primitives) and inlined
the flow-feature loader helpers into Mixed_CFM/data.py, then deleted
Unified_CFM/ entirely along with three dead aggregate shell scripts whose
referenced eval entry point (artifacts/verify_2026_04_24/) was already gone.

Verified: historic janus_iscxtor2016_seed42 checkpoint re-evaluated under
the absorbed code reproduces all 10 phase1 AUROC scores to 6 decimals;
same-seed retrain converges to within +/-0.001 on terminal_norm (residual
drift is CUDA non-determinism in MultiheadAttention + Sinkhorn argmax,
not the absorption).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Mixed_CFM/model.py

@@ -1,23 +1,14 @@
 from __future__ import annotations
 import math
+import sys as _sys
 from dataclasses import dataclass
+from pathlib import Path as _Path
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
-import importlib.util as _ilu
-import sys as _sys
-from pathlib import Path as _Path
-_UNIFIED_NAME = 'unified_cfm_model'
-if _UNIFIED_NAME not in _sys.modules:
-    _unified_spec = _ilu.spec_from_file_location(_UNIFIED_NAME, _Path(__file__).resolve().parents[1] / 'Unified_CFM' / 'model.py')
-    _unified = _ilu.module_from_spec(_unified_spec)
-    _sys.modules[_UNIFIED_NAME] = _unified
-    _unified_spec.loader.exec_module(_unified)
-else:
-    _unified = _sys.modules[_UNIFIED_NAME]
-AdaLNBlock = _unified.AdaLNBlock
-SinusoidalTimeEmb = _unified.SinusoidalTimeEmb
-_sinkhorn_coupling = _unified._sinkhorn_coupling
+
+_sys.path.insert(0, str(_Path(__file__).resolve().parent))
+from _layers import AdaLNBlock, SinusoidalTimeEmb, _sinkhorn_coupling
 
 
 @dataclass