Standard CRX over-approximates when Hasse diagram is non-linear (24% of
RAGSAK packages). Cluster-then-infer groups sequences by (first, last,
length), infers per-cluster, picks largest cluster's grammar.
Results on RAGSAK:
Avg max disjunction: 2.8 → 1.7 (39% tighter)
Packages improved: 6/10
Tradeoff: cluster granularity (too coarse = over-approximation,
too fine = no generalization). Current: (first, last, length_bucket).
Exports crx_refined() and crx_with_confidence() from bex package.
20 new tests. All 199 tests pass.
Sweet spot: 0.01-0.05. At 0.01 RAGSAK gets 61 SOREs (26.1% cov) with
real conventions like warn.status.body.ErrorResponse. At 0.05 coverage
jumps to 45.4% but that pattern disappears. Flask dies at 0.15+.
Current default min_coverage=0.2 is too aggressive for most codebases.
