Imported from silversight-578413a4/orx/sidon-sofa-coloring-direction-a-finite-sidon-sofas-a-n-28a68926:
- encoder_q16.py: Exact Q16_16 fixed-point DNA encoder (replaces float-based pipeline)
- padic_encoder.py: P-adic valuation encoder via CRT prime partial logarithms
These encoders enable the T6_dna test in photonic_sidon_search.py to pass,
bringing the full test suite to 18 PASS, 0 FAIL.
