nx_ship_fleet_gate.nx

nx_ship_fleet_gate.nx -- bite-proves the PURE adaptive-concurrency core in nx_shipfleet_lib.nx: the AIMD cap state machine (additive-increase +1 on progress, multiplicative-decrease halve on a storm, ceilinged by the polite budget, floored at 1) and the effective-width gate (pause on serve-first or admission-deny, else min(budget,cap)). The DRIVER's fork/wait4 pool is I/O and cannot be unit-tested here; the load-bearing DECISIONS are pure and are all tested. Every tooth is an equality on a pure function, so a mutant that (a) grows on a storm, (b) ignores the ceiling, (c) drops below 1, or (d) launches while serving/refused is KILLED. license_tier: ORIGINAL evidence -> stdout + verdict line (exit code carries the verdict via gv_verdict).