[wieslawsoltes]

Problem and change

DOMPurify captures Document.prototype.createNodeIterator; its absence blocked unchanged Code OSS chat rendering.

This change adds root-bounded document-order NodeIterator traversal, lazy filter and mask semantics, forward/backward state, mutation coverage, a DOMPurify-shaped native contract, an unchanged hash-pinned WPT, and a bounded 50,000-node linear performance gate.

Closes #82. Equivalent runtime and test changes remain in draft consolidation PR #76.

Validation

• One focused implementation commit on current main at 8baff8ae; exact head a459e0fd
• Release V8 native engine build
• Focused node-iterator contract: 10/10 local passes; warm runs 48-51 ms
• Required dom-treewalker-nodefilter-focus-navigation profile: 1/1 document, 6/6 subtests
• Required unchanged NodeIterator-removal-during-filtering WPT: 1/1 document, 4/4 subtests
• git diff --check

Native GitHub stack #158

1. Implement NodeIterator for DOM traversal #127 — current implementation layer — NodeIterator (Implement NodeIterator for DOMPurify and Code OSS chat rendering #82)
2. Isolate the NodeIterator stress fixture #129 — cumulative top — isolated scaling and memory gate (Isolate 50k NodeIterator stress fixture from Windows PartitionAlloc suite state #85)

Only the cumulative top PR receives remote validation. Merge both layers atomically through Stack #158 after the top related check passes.