Capture M16 gap execution artifacts

docs/status/M16-GAP-00174.md

@@ -0,0 +1,18 @@
+# M16-GAP-00174 Status
+
+status: in_progress
+task: anim.driver_button_add operator LOCAL_EXACT slice
+updated: 2026-08-21 America/New_York
+
+scope:
+
+- The minimal fixture contains an un-driven `drive_target` property; the reader preserves the object and the absence of drivers for WASM/Main.
+
+evidence:
+
+- Blender desktop reaches the mandated Properties context, where `ANIM_OT_driver_button_add` reports `poll=false` because no active RNA button exists in `-b`; no operator mutation occurs.
+- Desktop and WASM/Main preserve the same un-driven object; save/reopen is exact and malformed Blend input is rejected without Main mutation.
+- Fixture generation, desktop checker, npm comparator, direct comparator, and artifact hashing passed.
+- Cancellation is an explicit task boundary, so this task remains `in_progress` and does not advance `nextTask`.
+
+nextTask: `M16-GAP-00174`