Real cryptographic hashing, and twenty more Web APIs that actually do something

This release widens the Web API surface with members that carry real behaviour rather than empty placeholders. The headline is genuine cryptographic hashing: crypto.subtle.digest now computes SHA-1, SHA-256, SHA-384 and SHA-512, written from the standard and checked byte-for-byte against the published test vectors, so subresource-integrity checks, content-addressed caches and signature libraries that call it directly now get the right answer instead of a broken fallback. Alongside it: a real document node iterator that walks the page in order and filters by node type (how highlighters and reading-time estimators traverse text), the structured user-agent data and clipboard and media-device entries sites feature-detect through, the visual viewport object sticky headers read, a readable heap figure performance budgets look at, the Option, Audio, Path2D and BroadcastChannel constructors, the element fullscreen and pointer-capture methods drag and video controllers call, the legacy execCommand editing interface, and the stream queuing strategies. The measured Web API surface rises from 496 to 516 of 577 (86 to 89 percent). The engine gate holds at 6375 of 6375 and every addition carries a test - the four hashes against their known answers, the iterator against exact expected sequences.