Absence crosses the wire as a missing field: an omitted argument and a void
or undefined result both arrive as an absent JSON member, and the wide RPC
result slot accepts a success response without a value. Parameters declared
optional stay optional in the generated consumer declaration, so a business
signature is never widened to `T | undefined` to suit the wire. The weak SRC
descriptor reads parameter names from a JavaScript signature and cannot see
optionality, so a source-launched Host accepts an absent field and the strict
LIB pass owns rejecting a genuinely missing required parameter.
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