nx_isotope_ingest.nx

nx_isotope_ingest.nx -- chemistry external-reference loop, ingest stage. Reads the FOUNDATIONED NIST Atomic Weights data (knowledge/fetched/nist/atomic_weights.raw, CID'd + signed by nx_isotope_foundation) and MECHANICALLY extracts each isotope's (Atomic Number Z, Mass Number A, Relative Atomic Mass) from the "key = value" records, converting the mass to Q4 micro-AMU (mass*10000, rounded) to match our periodic table's iso_mass_q4 scaling. Writes a content-addressed canonical record per isotope into the sovereign seg_store (prefix knowledge/store/isotope-, key "iso:<Z>:<A>") -- the SSOT, NOT a TSV. Parse: a record's "Relative Atomic Mass =" line always follows its "Atomic Number =" and "Mass Number =" lines, so we carry cur_z/cur_a and emit on the mass line. Value like "15.99491461957(72)" -> stop at '(', Q4 = int*10000 + 4 decimals + round(5th). Baked self-test: iso:1:1 -> 10078 (H-1), iso:6:12 -> 120000 (C-12 exactly). license_tier: ORIGINAL