v0.26.4

Added

• TestEveryRequiredNameIsDeclared — a schema that lists a name in required
  without declaring it in properties makes a strict client refuse the whole
  tool list (Vertex AI: "schema at top-level requires unspecified property").
  data-toolbox-mcp shipped exactly that and broke a session outright; the
  existing contract test checked declared ⇒ required only, so the fleet is
  pinned in both directions now.