nx_symdrop_gate.nx

nx_symdrop_gate.nx -- proves the symbol-drop guard actually DETECTS a drop, and does not cry wolf. The tooth that matters is T5: a baseline symbol that is GONE from the current file must be reported. A guard that never fires is indistinguishable from no guard at all, and this one exists precisely because the failure it watches for (a stale whole-file write-back erasing a landed fix) leaves every other signal GREEN. So the fixtures below feed it a real removal and demand the alarm. The mirror teeth matter as much: additions and reorderings must NOT fire, or the sweep row goes RED on every normal edit and gets muted -- a muted alarm is worse than none. license_tier: ORIGINAL No hw writes (Rule 26). expect_exit: 0