CVE-2026-113897 PoC scaffold

WebKit Process Model — WebContent sandbox escape. Exercises the two suspected pre-fix trust bugs described in REPORT.md §3.2 / §3.3:

1. SharedMemory size mismatch — allocate an SAB, then post a "share" message whose declared byteLength exceeds the real size.
2. Crafted resource path / port name — trigger a resource load whose URL forces WebContent to construct a path-like or port-like string, then forward it to the auxiliary-process handler.