Add Chromium-only Blender WebEngine parity work

docs/status/W-018.md

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+# W-018 Status
+
+status: done
+task: 定义 Blender 风格 UI 协议和上下文
+
+## Evidence
+
+- Protocol: `web/protocol/ui-schema.ts`
+- Golden: `tests/golden/W-018/ui-schema.json`
+- State includes versioned Workspace/Area/Region layout, active Editor,
+  Blender mode, active object, selection, view layer, pinned data and revision.
+- `reduceUICommand()` keeps UI revisions separate from EngineWorker revisions.
+
+## Verification
+
+```text
+npm run typecheck  # passed
+npm run lint       # passed
+npm run build      # passed
+npm run test:e2e   # 3 passed
+```