audit: classify 117 FFI/systems unsafe findings as legitimate (PA001/PA007)

panic-attack assail flags 117 UnsafeCode/UnsafeFFI Critical/High findings
under cartridges/ — all at the C-ABI / syscall / kernel boundary.

Rationale: boj-server's cartridges/ tree contains ~114 MCP (Model Context Protocol) cartridges, each with an identical ffi/cartridge_shim.zig that wraps the cartridge's host-side C ABI. Every cartridge_shim.zig has the same pattern: extern C declarations + an unsafe pointer cast for the cartridge handle. These are all at the C-ABI boundary and required by Zig to call across.

Adds:
- audits/assail-classifications.a2ml (entries=117, classification=legitimate-ffi)
- audits/audit-ffi-2026-05-26.md

Anti-gameability: registry is separate from source under scan; new unsafe
inside a classified root requires a companion classification entry.

Refs hyperpolymath/panic-attack#32 (estate sweep tracker).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath