Add macOS local edge runbook

[aronchick]

Summary

• add a macOS runner for a locally bootstrapped expanso-edge agent
• load repo-local .env values for API and bootstrap credentials without checking secrets in
• support foreground checks, bootstrap, stop, and tmux-backed background execution with an explicit edge data directory
• add a five-node local cluster helper for Mac-native demos without Proxmox, Docker, or Linux VMs
• document bootstrap, run, stop, logs, cluster status, and direct CLI verification steps

Verification

• bash -n scripts/run-local-macos.sh scripts/run-local-cluster-macos.sh
• shellcheck scripts/run-local-macos.sh scripts/run-local-cluster-macos.sh
• git diff --check
• ./scripts/run-local-cluster-macos.sh --status
• expanso-cli node list --endpoint "$EXPANSO_CLI_ENDPOINT" --api-key "$EXPANSO_CLI_API_KEY" --format json --wide

Live verification on macOS showed five repo-local nodes connected to wkshc0olk1al7b.us2.cloud.expanso.io with agent version v2.1.18:

Name	Node ID	API
demo-jetpack-expanso-local	77fcb4ae-95ca-4c95-b20c-5a5ccdc5d7d0	localhost:9011
demo-jetpack-expanso-node-02	b01e3a7d-a3fe-4207-ac4e-e4885336afd0	localhost:9012
demo-jetpack-expanso-node-03	1a335eb9-ef6d-447c-b532-5ff2cd339ac3	localhost:9013
demo-jetpack-expanso-node-04	37761aca-e565-4613-8575-98fb6ee39015	localhost:9014
demo-jetpack-expanso-node-05	965e0ce5-7c52-42b5-826e-ffb0f480af49	localhost:9015