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/parity_caveats.py

@@ -24,19 +24,7 @@ re-triaged when the row moves.
 """
 
 # case id -> {aspect: "reason (ref: RSYNC_COMPAT.md ...)"}
-CAVEATS = {
-    # --max-delete stops the extras walk part-way and exits 25 in both
-    # implementations; which of the remaining extras survives depends on
-    # deletion order, which neither tool specifies.  The exit code and the
-    # number of survivors match (asserted implicitly by the harness's rc
-    # comparison and the one-for-one diff below).
-    "max_delete": {
-        "tree": "which destination extras survive a partial --max-delete abort "
-                "is deletion-order dependent and unspecified; rc=25 and the "
-                "number of survivors match rsync. ref: RSYNC_COMPAT.md "
-                "`--max-delete=NUM` row.",
-    },
-}
+CAVEATS = {}
 
 # Accepted aspect names (guards against typos in this file).
 ASPECTS = ("tree", "stdout", "extra", "rc")