feat: crib-anchored scoring + Bifid gather-variant coverage - #4
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Two general capabilities distilled from fractionation cryptanalysis work: * crib_anchor: score a guessed crib's best-over-position appearance in a decoded candidate, to anchor an SA objective when the plaintext register (terse, name-heavy, numeric) defeats n-gram fitness. Decoder-agnostic; carries the calibration guidance as code (SWEET_SPOT, crib_length_advice): a short crib floods, an over-long one won't converge, one contiguous ~16-20 letter crib is the sweet spot. * fractionation: bifid6 now takes a `gather` read-order parameter across encode/decode/solve_bifid6 with GATHER_VARIANTS (all 8 seriation orders); the "std" default is fully backward-compatible. Closes a silent-miss blind spot -- several read-orders are statistically indistinguishable, so a solver assuming only the standard order fails quietly on the others. Tested: round-trips for all 8 gather variants, std backward-compat, crib-anchor unit + behavioral. ruff/mypy clean. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EJjjwhsWqwb5GRvD4QiA5i
Pre-existing formatting drift (byte-identical to main): the repo's `ruff format --check .` now formats fenced code blocks in markdown, and this docs file predates that. Whitespace-only — blank line after import, single space before inline comments. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EJjjwhsWqwb5GRvD4QiA5i
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Two general capabilities distilled from fractionation cryptanalysis work:
crib_anchor: score a guessed crib's best-over-position appearance in a decoded candidate, to anchor an SA objective when the plaintext register (terse, name-heavy, numeric) defeats n-gram fitness. Decoder-agnostic; carries the calibration guidance as code (SWEET_SPOT, crib_length_advice): a short crib floods, an over-long one won't converge, one contiguous ~16-20 letter crib is the sweet spot.
fractionation: bifid6 now takes a
gatherread-order parameter across encode/decode/solve_bifid6 with GATHER_VARIANTS (all 8 seriation orders); the "std" default is fully backward-compatible. Closes a silent-miss blind spot -- several read-orders are statistically indistinguishable, so a solver assuming only the standard order fails quietly on the others.Tested: round-trips for all 8 gather variants, std backward-compat, crib-anchor unit + behavioral. ruff/mypy clean.
Claude-Session: https://claude.ai/code/session_01EJjjwhsWqwb5GRvD4QiA5i