nx_state_spool_core.nx

nx_state_spool_core.nx -- importable CORE of the STORE-AND-FORWARD state spool (CR-R1a of the crash-resume->SOTA roadmap, amended 07-15 by operator directive: "the hub is the NAS not the laptop; the laptop when on network should sync to the NAS as much as possible; when the NAS isn't available it should go local"). Semantics: capture writes are NAS-FIRST -- a line is spooled locally, then DRAIN attempts delivery via a PLUGGABLE transport ELF (argv[1]=line, exit 0 = delivered); delivered lines leave the spool, failed lines are KEPT (offline = nothing lost) without blocking later lines (head-of-line non-blocking; state lines are latest-wins). Durability: spool ops serialize under a sidecar flock; drain rewrites via tmp + renameat (atomic -- a crash mid-drain leaves the old spool or the new one, never a torn file). Transport is a parameter so the gate proves the semantics OFFLINE; CR-R1 plugs the real NAS API poster in without touching these mechanics. license_tier: ORIGINAL