refactor(observation): separate capture coordination from document consistency

apps/extension/src/tools/vom/normalize.ts

@@ -34,7 +34,6 @@ export interface FrameContext {
 export interface NormalizedDocument {
   nodes: NodeFacts[];
   index: DocumentIndex;
-  documentElementBackendNodeId?: number;
 }
 
 /** Interpret one document using a supplied projection. No live reads or frame scheduling. */
@@ -95,12 +94,6 @@ export async function normalizeDocument(
       (node) => !node.tag.startsWith("#") && !index.excludedBackendNodeIds.has(node.backendNodeId),
     ),
     index,
-    documentElementBackendNodeId: nodes.find(
-      (node) =>
-        node.nodeType === 1 &&
-        node.parentBackendNodeId !== null &&
-        index.nodes.get(node.parentBackendNodeId)?.nodeType === 9,
-    )?.backendNodeId,
   };
 }