Port seq_monadic to the split_set branch, reimplemented against the
cont_regex / split / split_manager API. Element-sort agnostic: relies on
the derivative engine and th_rewriter, no character-specific reasoning.
- Global derivative-transition graph reused across regexes (intern_state /
expand_state / build_graph) so states, nullability and cofactor successors
are computed once.
- embed(r) = <concat(r, epsilon), epsilon>; the epsilon accept-state marks the
membership (nullable) case uniformly.
- intersect handles general cont_regex, including non-epsilon reach targets N
(membership BFS + product-reachability paths).
- No budget / reset_pin.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 34aa9af0-4977-411d-aaa7-7cb81cc4e9f8
