CVE-2026-83612: xmldom: HTML raw-text closing-tag case mismatch causes output amplification

In HTML mode (text/html), a raw-text element (script, style, textarea, title) whose closing tag differs in case from its opening tag (e.g. </ScRiPt> for <script>) is mishandled by the parser, producing quadratic (O(n²)) output growth — a small crafted document parses and serializes into output orders of magnitude larger, exhausting CPU and memory. A modest input of tens of KB can therefore cause a denial of service in any service that parses untrusted HTML with xmldom. Only HTML mode is affected.