Compiled --ref-asm: value-call ignores a value-type default parameter

[nickna]

Summary

Follow-up to #705 (case b). In --compile --ref-asm (reference-assembly emit) mode, calling a function expression / arrow as a value does not apply a value-type parameter default for an omitted argument. Plain --compile and the interpreter are correct.

Repro

const f = function (x: number, y: number = 3) { return x + y; };
console.log(f(4));

mode	result
interpreter	7
--compile	7
--compile --ref-asm	3 ← BUG (default y = 3 not applied, y is 0)

Notes

• Pre-existing and independent of Compiled: value-type default parameters cannot represent an explicit/padded undefined (yields NaN) #705's fix: Compiled: function expressions / arrow functions ignore default parameter values for omitted arguments #646 already widened arrow/function-expression defaulted params to an object slot, and plain --compile applies the default via the entry prologue. The --ref-asm value-call path does not. (Before Compiled: function expressions / arrow functions ignore default parameter values for omitted arguments #646 this same case produced an invalid-IL StackUnexpected error, so --ref-asm was already broken here.)
• Audit the --ref-asm value-call dispatch for widened object params — the omitted slot is not being padded with the $Undefined sentinel (or the entry prologue is not reached) on that path.

Discovered

While implementing #705.

[nickna]

Verified resolved on main (e8f3990): compile --ref-asm value-call applies the value-type default (f(4)=>7), matching --compile and the interpreter. Implemented in #787 (the $ExpectsThis marker attribute).