One public knob fanning into >=2 sibling params: Gang/GangMember types
(the Role name/targets split + BoundParam pos/name dual), Composite.gangs
behind the single fallible Composite::with_gangs gate, check_gangs as the
shared $A predicate (all three future minting boundaries route here), and
CompileError::BadGang(GangFault) as the typed refusal.
PrimitiveBuilder::original_pos (aura-core) extracts bind's pos-reconstruction
loop verbatim so gang members and BoundParam share one coordinate space.
Deviation ratified vs the plan: GangFault::KindMismatch carries structural
{node, name} coordinates instead of a stringly member label, consistent with
the sibling arms (plan amended). A redundant test-local fixture wrapper was
dropped after a fresh quality re-review of the blocked task diff.
Verified: cargo test -p aura-engine --lib 249/0, -p aura-core 53/0, clippy
-D warnings clean on both crates.
refs #61
Brummel
5eedf060dd