Model UnlinkPool hashNote via PoseidonT4 boundary

[Th0rgal]

Summary

• add a linked PoseidonT4 boundary alongside the existing PoseidonT3 boundary
• route hashNote through poseidonT4(npk, uint160(token), amount) instead of placeholder arithmetic
• refresh the build_green task notes to reflect the remaining manifest blockers

Verification

• git diff --check
• lake build Benchmark.Cases.UnlinkXyz.Pool.Compile Benchmark.Generated.UnlinkXyz.Pool.Tasks.BuildGreen

---

Note

Medium Risk
Updates the UnlinkPool model’s note hashing from placeholder arithmetic to a new poseidonT4 external boundary, which can affect any logic/proofs depending on commitment values. Remaining changes are task/manifest metadata updates with low runtime impact.

Overview
Models UnlinkPool.hashNote as a real cryptographic boundary call by adding a linked external poseidonT4 and routing hashNote(npk, token, amount) through poseidonT4(npk, uint160(token), amount) instead of placeholder math.

Refreshes the build_green task template and manifest notes to reflect the updated state of the translation and to track remaining unsupported-feature blockers (including new entries for proxy storage rotation and assumed cryptographic/Permit2/Groth16 axioms).

^{Reviewed by Cursor Bugbot for commit 7859c8d. Bugbot is set up for automated code reviews on this repo. Configure here.}