Fix determinism workflow: compare hashes only, not file paths

The diff was failing because sha256sum output includes file paths
(out1/ vs out2/) which always differ. Extract just the hash values
for comparison. Also make cross-platform diff a hard failure.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: AngeloTadeucci

.github/workflows/determinism.yml

@@ -40,12 +40,12 @@ jobs:
       - name: Hash outputs
         shell: bash
         run: |
-          sha256sum out1/Test.m2d out1/Test.m2h > hashes-run1.txt
-          sha256sum out2/Test.m2d out2/Test.m2h > hashes-run2.txt
+          sha256sum out1/Test.m2d out1/Test.m2h | tee hashes-run1-full.txt | awk '{print $1}' > hashes-run1.txt
+          sha256sum out2/Test.m2d out2/Test.m2h | tee hashes-run2-full.txt | awk '{print $1}' > hashes-run2.txt
           echo "=== Run 1 ==="
-          cat hashes-run1.txt
+          cat hashes-run1-full.txt
           echo "=== Run 2 ==="
-          cat hashes-run2.txt
+          cat hashes-run2-full.txt
 
       - name: Verify same-platform determinism
         shell: bash
@@ -93,8 +93,8 @@ jobs:
           cat linux/hashes-run1.txt
           echo "=== Diff ==="
           if diff win/hashes-run1.txt linux/hashes-run1.txt; then
-            echo "PASS: Cross-platform archives are identical"
+            echo "PASS: Cross-platform archives are byte-identical!"
           else
-            echo "INFO: Cross-platform archives differ (expected due to native zlib differences)"
-            echo "This is not a failure — see workflow summary for details."
+            echo "FAIL: Cross-platform archives differ"
+            exit 1
           fi