test(parity): assert max_delete invariants, empty the parity allowlist

The max_delete case allowlisted the tree aspect because the surviving extras after a partial --max-delete abort are deletion-order dependent. Under FASTSYNC_PARITY_STRICT a run where the orders coincide was reported as a stale entry (CI failure), while removing the entry made the order-dependent tree mismatch fail. Add a per-case 'compare_tree' flag: max_delete now asserts rc=25 plus the survivor count via extra_check instead of exact tree identity, so the allowlist can be empty. Burn-down reached zero.

tests/integration/test_differential_parity.py

@@ -207,7 +207,8 @@ _CASES = [
            seed=seed_delete_excluded, server_args=DELETE, ref="--delete-excluded"),
     H.Case("max_delete", "basic", ["-a", "--delete", "--max-delete=1"],
            seed=seed_max_delete, server_args=DELETE,
-           extra_check=max_delete_count_check, ref="--max-delete"),
+           extra_check=max_delete_count_check, compare_tree=False,
+           ref="--max-delete"),
 
     # --- relative / dirs --------------------------------------------------
     H.Case("relative_general", "basic", ["-a", "-R"], layout=H.MIRROR_ABS,