Continue Blender Web parity task handoff

docs/status/M16-GAP-00229.md

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+# M16-GAP-00229 Status
+
+status: done
+task: armature.collection_show_all operator LOCAL_EXACT slice
+updated: 2026-08-22 America/New_York
+
+scope:
+
+- The minimal fixture contains three bone collections, with the middle collection hidden and one distinct bone assigned to each collection.
+- Desktop runs `ARMATURE_OT_collection_show_all` with `poll=true` and `FINISHED`, setting every collection visible while preserving collection order and membership through save/reopen.
+- The Main reader exposes each armature `boneCollections` entry's `visible` flag from `BONE_COLLECTION_VISIBLE`; no other data-block, editor, or browser behavior was added.
+
+evidence:
+
+- The generator, desktop checker, npm comparator, direct comparator, and task-context checks passed. Repeated checker runs recognize the already-visible collections and remain idempotent.
+- WASM/Main observes all three collections as visible with matching member bone IDs, preserves them across save/reopen, and rejects malformed Blend input without Main mutation.
+- Chromium-only policy was preserved; no Firefox/WebKit run was made.
+
+nextTask: `M16-GAP-00230`