The current TERPSICHORE-native migration slice already covers the reduced internal-region stability path, but it does not yet correctly establish the first wall-coupled external-region capability needed for vacuum plus conducting wall analysis.
Read the provided method context and source snapshot, run the public reproduction, and complete the missing capability so the implementation no longer behaves like an internal-only scaffold when a vacuum region and an explicit conducting wall are part of the problem. A correct solution should let materially different conducting walls produce distinct global potential-energy and stability observations while the no-explicit-wall fallback remains available.
Constraints:
- keep the solution generic and array-based;
- do not hard-code the public reproduction values;
- preserve the no-explicit-wall fallback path;
- keep the public reproduction runnable without internet access.