nx_shelf_life.nx

nx_shelf_life.nx -- FOOD-SCIENCE SUITE / SHELF-LIFE rung. Accelerated shelf-life testing (ASLT) via the Q10 model, plus a cold-chain breach accumulator that tracks the FRACTION of shelf life a product consumes across its real temperature history -- so "best by" reflects how the food was actually stored, not a fixed date. Q10 = ratio by which the quality-loss RATE changes per 10 C. Shelf life scales as Q10^(-dT/10): 10 C warmer -> life / Q10; 10 C colder -> life x Q10. INTEGER-EXACT at decade steps (same powers-of-integer trick as the preservation z-value). THE exceed: a printed date assumes one storage temperature forever. This computes life at any decade temperature AND accumulates consumed life across segments, so a cold-chain breach shortens the remaining date by construction (fraction consumed >= 1.000 -> expired). ===== THE DECADE-ONLY GAP, NOW CLOSED ============================ sl_at_temp returns -1 for any temperature difference that is not a multiple of 10 C. That was documented as an honest gap, but it made the organ unable to answer the question the whole category rests on: ICH stability compares 25 C with 40 C, a FIFTEEN degree gap. The organ refused the one comparison that matters commercially. sl_at_temp_frac closes it by moving into decade-log space, where a fractional power is just a multiplication: Q10^(-dT/10) = 10^(-dT*log10(Q10)/10) Both halves already existed in nx_pow10 (this suite's own shared numeric rung), so this is a CHANGE OF VARIABLE, not a second model. ADDITIVE, per the API-stability rule: sl_at_temp is untouched and every existing caller and test is unaffected. Where both are defined the new path DELEGATES to the exact integer one -- an interpolated logarithm is never better than exact repeated multiplication. sl_scale_frac_q3 is exposed separately so the gate can compare the interpolated path against the exact one head-on; testing only the dispatcher would pass vacuously at decade steps by measuring the exact path twice. grounded: q10_accelerated_shelf_life_testing + arrhenius_food_quality_kinetics genealogy_id: aslt_q10_model + nishi_food_science_suite