Perf/dlmalloc guest allocator

.github/workflows/pr_main.yaml

@@ -158,9 +158,14 @@ jobs:
       - name: Run CLI tests
         run: cargo test -p cli
 
-      - name: Run syscalls host tests (keccak differential vs sha3)
+      - name: Run syscalls host tests (allocator + keccak differential vs sha3)
         run: make test-syscalls
 
+      # The dlmalloc fallback is feature-selected, so nothing else in CI compiles it and it
+      # can rot silently. Its tests run here too.
+      - name: Test the dlmalloc guest allocator fallback
+        run: cd syscalls && cargo test --features dlmalloc-alloc
+
   # "Test" is a required check — keep this name to avoid branch protection changes.
   # This gate job passes only when CLI, executor, disk-spill, and prover tests succeed.
   test: