Add script execution to the page loading pipeline: after HTML parsing, walk the DOM for <script> elements and execute them in a shared JS VM with full DOM access. Scripts can modify the DOM before CSS/image collection. Key changes: - New script_loader module: discovers scripts in document order, fetches external scripts, handles defer/async/type attributes - VM.detach_document(): reclaim Document after script execution - Top-level var declarations now emit StoreGlobal so variables persist across multiple execute() calls (shared global scope) - Resource::Script variant for JavaScript MIME types - Exhaustive match updates in css_loader and img_loader Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>