test: explicitly repin validation to reviewed channel source

tests/validation/re100_helpers.py

@@ -1,7 +1,8 @@
 """DFG Re100 periodic reference comparison with declared pressure-NEQ outlet, not exact do-nothing.
 
-CPU helpers import without CUDA. GPU execution uses unchanged d79e3f6 production
-sources. Default pilot is deliberately too short to certify periodic convergence.
+CPU helpers import without CUDA. GPU execution verifies the explicitly pinned
+AMR-channel experimental source snapshot. Historical d79 evidence remains tied to
+its original commits. Default pilot is too short to certify periodic convergence.
 """
 
 import argparse
@@ -16,7 +17,7 @@ from tempfile import TemporaryDirectory
 import numpy as np
 
 ROOT = Path(__file__).resolve().parents[2]
-PIN = "d79e3f6f0a424f5bcc3a1a6d610313e49daf97a2"
+PIN = "47b05bc8abfc957fe876b0c63bdb386e3c6cbaa5"
 
 
 def geometry(n):