v1.108.157 — order() moves a multi-item list on a singular prop to its plural

Follow-up to v1.108.156, surfaced by the post-fix benchmark rerun: order("get_symbol_source", {"symbol_id": [a, b, c]}) raised TypeError unhashable-list downstream — symbol_id IS a declared property, so the near-miss key mapping skipped it. A multi-item list on a singular string-typed prop whose plural sibling is a declared array (and not already provided) now moves to the plural. Single-item lists keep the existing unwrap; an explicitly-provided plural is never clobbered.

No schema, tool-count, or INDEX_VERSION change. +2 tests in tests/test_v1_108_156.py.