B7: LD-SDA research extensions and gdpopt.ldbd

[bernalde]

Registration/vestigial-code bugs filed upstream (Pyomo#4015). The research-sized remainder:

• Dual bounds: LD-SDA is primal-only — pair with a bounding companion (pseudo-basic-step bounds from A2, or LBB dual info).
• Generalize beyond Exactly(1) (ldsda.py:319-322) and auto-discover reformulable logical constraints (:309-312 — starting-point linkage problem).
• Z3 neighbor pruning (see B4).
• gdpopt.ldbd: Liñán & Ricardez-Sandoval, AIChE J 69:e18008 (2023), https://doi.org/10.1002/aic.18008 + 2024 multicut follow-up (aic.18491) — logic-based discrete Benders over the same external-variable reformulation; paper code only, natural GDPopt companion algorithm.

Part of roadmap epic #2 (item B7).