Add AArch64 support to semantic function extraction

[haasonsaas]

Context

Semantic extraction is currently implemented around iced-x86 and documents x86-64 as the only supported architecture. That excludes native Apple Silicon and a large share of modern Linux malware and software.

Proposal

Introduce an architecture-specific disassembly interface and add an AArch64 implementation behind an explicit extractor version. Keep unsupported architectures as honest limitation records rather than silently producing incomparable features.

Acceptance criteria

• PE/ELF/Mach-O AArch64 fixtures can be classified and semantically extracted.
• AArch64 features cannot be compared with x86-64 features unless the model explicitly allows it.
• Architecture and decoder version are persisted in feature and edge evidence.
• Malformed and mixed/fat binaries produce bounded limitation records.

References

• x86-only design decision
• function extraction module
• feature extraction