v0.3.0 — mature engines

v0.3.0 swaps the hand-rolled internals for battle-tested engines when installed, keeping the pure-Python core as fallback.

Added

• Optional backends: capstone (disasm), unicorn (real CPU emulation), lief (PE/ELF/Mach-O). pip install "reverify[full]"; reverify backends shows what's active.
• Unified reverify parse for PE / ELF / Mach-O (arch, entry, sections, imports, exports).
• Real x86/x64/ARM/ARM64 emulation via Unicorn; emulate --backend.
• New verifier claim kinds: import_present, export_present, section_present.

96 tests, gated to pass with or without the engines. pip install reverify