Continue Blender Web parity task handoff

docs/status/M16-GAP-00263.md

@@ -0,0 +1,24 @@
+# M16-GAP-00263 Status
+
+status: done
+task: armature.symmetrize operator LOCAL_EXACT slice
+updated: 2026-08-23 America/New_York
+
+scope:
+
+- The fixture contains one selected positive-X `WebGapArmatureSymmetrizeSource.L`
+  bone and one unrelated unselected bone. Blender desktop runs
+  `ARMATURE_OT_symmetrize(direction="NEGATIVE_X")`, producing the mirrored
+  `WebGapArmatureSymmetrizeSource.R` bone and preserving the result through
+  save/reopen.
+- WASM/Main reads the same armature. The comparator confirms mirrored geometry,
+  selection state, malformed-input rejection without Main mutation, and
+  save/reopen.
+
+evidence:
+
+- Fixture generation, desktop checker, npm comparator, and direct comparator
+  passed with exit code 0. Chromium-only policy was preserved and no
+  Firefox/WebKit run was made.
+
+nextTask: `M16-GAP-00264`