buildhost: old-mac-build-host (private)

Owns the machines: build minis, toolchains, inventory, disaster recovery, the canonical pickers (scripts/pick-build-host.sh, scripts/pick-bench-host.sh), shared scripts (synced by scripts/sync-shared-scripts.sh --write), Jenkins jobs, and bench-evidence.sh/bench-compare.sh. Builds no game.

• Serve port owners: diagnose tooling blockers, return a concrete next step, fix shared tooling here with evidence. Ports keep engine changes and measurements.
• Edit shared scripts only here, then sync. Never edit a port's copy.
• After any picker or lock change run tests/test-bench-lock.sh and quote its output.
• Install tooling as needed; prefer static binaries in PATH over system libraries; record capability changes in docs/. Never risk an irreplaceable vintage OS install.