feat: allow omitted void modal input

[okyrychenko-dev]

Summary

• add ModalOpenArgs<TInput> to make input optional for modal definitions using void or undefined
• apply the conditional tuple consistently across modal managers, lifecycle APIs, registered definitions, and typed registries
• preserve required input arguments for every other input type
• preserve the inferred ModalHandle<TResult> return type when input is omitted
• verify both valid inputless calls and invalid missing-input calls through the packed-consumer typecheck
• update internal fixtures, stories, benchmarks, and documentation to use the shorter inputless syntax
• export ModalOpenArgs as part of the public type API
• introduce no ESLint suppressions, type assertions, any, or runtime behavior changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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