nx_replyreserve_gate.nx

nx_replyreserve_gate.nx -- GATE for the reply-reserve calibrator. Composes nx_replyreserve_lib and nx_loadceil_lib IN-PROCESS on PLANTED buffers, so every value is asserted with no real actlog and no forked binary. One real file is written, to a uniquely-named /tmp path this gate alone uses, because the tail-read tooth cannot be proven on a buffer -- it is a claim about lseek and a file. THE LOAD-BEARING TOOTH is not "a number came out". It is the pair that would let the trivial wrong implementation pass: a row on the right lane that carries NO reply_ms must count as MISSING, never as a zero sample. A collector that read an absent key as 0 would flood the distribution with zeros, drive the quantile to 0, and derive the floor -- a confident, wrong, and permanently-stable answer. The fixture carries 25 such rows and the gate asserts both the missing count AND that the minimum is not 0. NEG-CONTROLS: a reply_ms on a DIFFERENT lane must not enter the sample; too few samples must abstain and derive nothing; an empty buffer must be UNREADABLE and not a zero reserve; a reserve that reaches the window or the fraction cap must be REFUSED with the current value kept; a conf with no reserve row must refuse the rewrite rather than append a second row; and the whole-buffer conf reader must be shown to FAIL on the real conf shape, which is why the line-anchored one exists.