v1.0.0: macOS ARM64 support — Apple Silicon binaries + Homebrew formula

[MicBur]

Roadmap: v1.0.0

Native Apple Silicon (arm64) client & worker binaries and a Homebrew formula for 30-second install on macOS, matching the apt story on Linux.

Scope

• Build client + worker for arm64-apple-darwin (CMake toolchain, OpenSSL/zstd/sqlite via Homebrew or vendored)
• Homebrew formula (tap or core), brew install suco
• Smoke test: macOS client → Linux worker cross-dispatch; macOS-native compile + cache
• CI: add a macOS runner to the matrix

⛔ Blocked: no macOS build host available on the current machines (see brain-claude.md "Untested here"). Needs an Apple Silicon environment before it can start. Park until hardware exists.

Lane: cross-platform; blocked on environment.