Resolve a spec's params against the accumulated outputs (ref → its output map). Throws if a referenced output is missing (a producer that didn't emit the key) — fail-closed, never silently substitute undefined into a provider call.
Resolve a spec's params against the accumulated outputs (ref → its output map). Throws if a referenced output is missing (a producer that didn't emit the key) — fail-closed, never silently substitute undefined into a provider call.