Continue Blender Web parity task handoff

docs/status/M16-GAP-00175.md

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+# M16-GAP-00175 Status
+
+status: done
+task: anim.driver_button_edit operator LOCAL_EXACT slice
+updated: 2026-08-21 America/New_York
+
+scope:
+
+- The minimal fixture contains one scripted driver on `drive_target`; Blender desktop invokes `ANIM_OT_driver_button_edit` in the active Properties context (`poll=true`, `INTERFACE`) and preserves the driver without a Main mutation.
+
+evidence:
+
+- Desktop and WASM/Main expose the same driver (`["drive_target"]`, expression `frame * 2.5 + 1.25`, scripted, no variables); 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. The edit operator is intentionally interface-only and leaves the driver unchanged.
+
+nextTask: `M16-GAP-00176`