HermitCrab FST: two-pass nondeterministic traversal (rejected: 2.3x traversal instances, arc checks down only 1.6%) #596

A port of the investigate_linear_traverse approach. It first merged traversal instances by state, position and variable bindings, then rebuilt captures. It was removed from production.

Measured. On 45 Sena words it used 2.3 times as many traversal instances, cut arc checks by only 1.6%, produced more duplicate matches and raised word clones by 27%. Conformance fixtures pointed the same way.

Why rejected. HermitCrab's traversal already pools instances, and its patterns lack the repeated-group shape needed to repay the capture rebuild. Reopen only for a corpus whose automata have substantial equivalent active-state convergence, with a census showing that capture reconstruction is cheaper than the current traversal. See also the (State, AnnotationIndex) record, which drops bindings from the key and is unsound for the same captures.

Record: https://github.com/sillsdev/machine/blob/2eba2f502338705a4d529d7034cecb6303db7f35/docs/rejected-optimizations/two-pass-nondeterministic-traversal.md
Ledger: https://github.com/sillsdev/machine/blob/2eba2f502338705a4d529d7034cecb6303db7f35/docs/hermitcrab-optimization-ledger.md; disposition: https://github.com/sillsdev/machine/blob/2eba2f502338705a4d529d7034cecb6303db7f35/docs/hermitcrab-perf-2026-09-disposition.md
From #490 (closed).