Cover durable workflow query argument contracts

[rmcdaniel]

Summary

• exercise positional and named query arguments from persisted WorkflowStarted contracts
• cover defaults, variadics, unknown/excess arguments, nullability, unions, intersections, built-in and class types
• prove safe list/named fallbacks when neither durable metadata nor a loadable workflow definition supplies a contract

Verification

• 6 focused tests / 38 assertions pass
• Easy Coding Standard passes
• PHPStan passes for the new test
• public-boundary scan passes

Contributes to #426.