CVE-2018-4441 arbitrary read/write self-test

This preserves v259's initial layout and fetches the source-backed fake Uint32Array master/slave extension only after phase four succeeds, then reads and writes only a dedicated owned typed array.

Retire the Store process after every armed attempt, even after a reported miss. This test performs a malformed splice and relative OOB access.

One attempt only. This validates a table-dispatch entry and constant-return leaf, temporarily redirects one object header and one host-call pointer, invokes once, then restores both and verifies cleanup. No stack pivot, ROP chain, syscall, device access, or kernel operation.