Harden silent LPN parameter selection

[ladnir]

Summary

• harden Silent VOLE/LPN parameter selection using attack-aware floors plus pseudo-distance robustness
• use regular integer stationary noise where appropriate, restrict quasi-cyclic mode to binary fields, and fix truncation and packing edge cases
• add stationary OT state and coefficient mixing/constMul support for the existing extension fields
• make RingLPN c and t runtime parameters selected through the shared policy rather than compile-time protocol constants

Depends on #188. Review only the commits above codex/pr-dpf-infrastructure.

Silent OT and VOLE expand only the tree-output prefix of their buffers, then restore and zero encoder padding. This fixes the PPRF length rejection for padded configurations without changing the parameter policy or copying the expanded output. Size sweeps cover padded regular and stationary configurations.

Validation

• The full stack passed 318 Windows tests, with 24 disabled-configuration skips, including the previously failing Silent OT, AnyField F2 OLE, and RevCuckoo robustness cases.
• Expanded OT and VOLE size sweeps passed for padded requests and stationary noise.
• After the dependency fix, GCC 13/ASan passed 33 focused curve, base-OT, RingLPN, RevCuckoo, and AnyField tests (3 configuration skips). The 38,448-OT SimplestOT reproducer now has zero mismatches.
• Windows passed the added curve regression, existing hash-to-curve tests, and RingLPN base generation after the dependency update.
• The broader local GCC build has SoftSpoken disabled, so five VOLE tests requiring that backend cannot run successfully in that configuration. Silent OT is also disabled locally; its padding sweeps passed on Windows and in GitHub Ubuntu CI.
• Ubuntu/ASan and macOS CI passed on the preceding heads. Fresh CI is running for the final dependency update.