nx_capgraph_derive_lib.nx

nx_capgraph_derive_lib.nx -- pure core for nx_capgraph_derive: level thresholds, row parsing, the progress-rail snapshot compare, and the history reader. SPLIT OUT 2026-07-31 for the SAME reason as nx_capgraph_edges_lib: these helpers sat beside a main() and were therefore unreachable from any gate, which pinned the progress rail at level 2 (WORKS) on this system's own ladder. Gating the edges organ but not this one would have been applying the standard selectively -- exactly the kind of convenient inconsistency this arc exists to catch. license_tier: ORIGINAL No hw writes (Rule 26).