nx_debt_payoff.nx

nx_debt_payoff.nx -- R4 of THE NISHI FINANCIAL ECOSYSTEM: exact debt amortization + payoff strategy. ⚠NAME HISTORY (seq240/seq121, resolved 2026-07-23): this module was ONCE runtime/nx_debt.nx and COLLIDED with _hdl_build/nx_debt.nx (the debt-plane CLI). Because imports resolve dir-local and the build probes _hdl_build FIRST, every `import "nx_debt.nx"` from runtime/ silently resolved to the CLI -- which has no dbt_* symbols -- so the whole finance lane failed with `expand_imports failed`. The file is now nx_debt_payoff.nx and `nx_debt` unambiguously means the CLI. Do NOT reintroduce the name. Built on nx_money (no-float, exact i64 cents). This is the operator's MOST URGENT rung: HELOC + high-interest debt. Everything here is deterministic integer arithmetic -- an amortization schedule is just iterated (interest = round(balance * monthly_rate); principal = payment - interest) and is therefore bit-exact and reproducible (floats would drift cent-by-cent over hundreds of months). CAPABILITIES: dbt_payoff_months -- simulate one loan at a fixed payment -> months to payoff + total interest, and DETECT the minimum-payment trap (payment <= interest -> never amortizes). dbt_strategy -- multi-debt payoff under a fixed monthly budget, avalanche (highest-APR-first, interest-optimal) vs snowball (lowest-balance-first). Returns total months + total interest. The avalanche<=snowball interest fact is MEASURED by the gate. NEVER-BRICK FINANCIAL ANALOG (#26): no schedule can loop forever -- the minimum-payment trap is detected and reported (-1), an under-funded budget is rejected (-1), and a hard month cap (-2) is a defensive backstop. Nothing here mutates the caller's input arrays (strategy works on copies). license_tier: ORIGINAL