packTypeElems now handles a parameterized spread operand F(Ts): for each pack
element T_i it temporarily binds the pack name to T_i and resolves F(T_i),
yielding (VL(T0), VL(T1), ...). Combined with parameterized-protocol value
types, the canonical Combined struct field sources: (..VL(Ts)) now resolves to
a tuple of real protocol values.
End-to-end (examples/207): instantiate Combined(s64, s64, string), whole-store
c.sources = (xx IntCell, xx StrCell), and per-element dispatch c.sources.0.get()
/ c.sources.1.get() all work. 242 examples + unit green.
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