fix(aiur): replay constrained calls cached as hints

[arthurpaulino]

Unconstrained calls cache function queries with zero multiplicity. When a later constrained call reused the same query, the executors previously incremented only the cached callee row. They did not replay its body, so nested function, memory, and gadget lookup obligations could remain inactive. The resulting witness had unbalanced lookup channels and failed verification with UnbalancedChannel.

Treat a constrained cache hit with zero multiplicity as promotion: replay the callee body in constrained mode so activation recursively reaches its dependency tree. At return, reuse the existing query, assert that the recomputed output agrees with the cached hint, and increment its multiplicity instead of inserting a duplicate. Apply the same behavior to the bytecode executor and generated Rust executor, then regenerate both codegen outputs.

Add a focused Rust prove/verify regression and an aiur-prove case where an unconstrained call is followed by an identical constrained call whose callee performs a nested call. With the fix removed, both reproduce UnbalancedChannel; with the fix restored, they verify successfully.

Validation:

• lake exe ix codegen
• cargo clippy --release
• cargo test -p aiur --release prove_verify_promotes_nested_unconstrained_call -- --nocapture
• lake test -- aiur-prove
• lake test -- --ignored ixvm
• exact Nat.add_comm benchmark prove/verify path