protocol: principled exclusion note for the design-space x GSM8K matrix

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

results-loop/PROTOCOL_UNIFIED.md

@@ -336,3 +336,12 @@ levels — only seed means are.
     (c) overall never beats k=0. If hard exceeds 15% or overall beats
     k=0, task interference in the mixed run was masking a real GSM
     capability — would reopen the GSM chapter.
+
+    Scope note (item 17): the design-space arms of items 11-15 are NOT
+    crossed with GSM8K, deliberately. Exclusion by dominance: fidelity-
+    failing regimes (rec, parcae) cannot improve on a task MORE fidelity-
+    fragile than MBPP; architecture-failing (per-depth) and equivalent
+    (tied-alpha -> merge) and k-placement-only (randk) and same-family
+    (noise-s0, h2048) variants have no mechanism by which task change
+    could invert their MBPP verdict. Only the recipe family's best member
+    (this item) is informative on GSM8K.