A new conformance check catches the 2026-07-28 spec's deterministic tools/list ordering rule, which nothing tested before

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modelcontextprotocol/conformance#492 adds `tools-list-deterministic-order`, issuing three consecutive `tools/list` requests and emitting WARNING when the same multiset of tool names comes back in a different order. The requirement is new in the 2026-07-28 revision (absent from 2025-11-25), introduced by modelcontextprotocol#2516 and motivated by client-side tool-list caching and LLM prompt-cache hit rates. The check reports untestable when the tool set changed between probes, since the spec scopes the SHOULD to an unchanged set, and a negative fixture server that rotates its list by one position on every call proves it fires.