monitor-exporter: install script, ship it in the zip, bump to 1.7.0

[evandhoffman]

Follow-up to #58 / #59: make the exporter a compiled binary you install and run, not swift run, and cut the minor release the feature earns.

What's here

• Scripts/install-exporter.sh — one command from a checkout or an unpacked release zip to a running service. It finds a binary (the signed one beside it in a zip, or a fresh -c release build in a checkout), installs the compiled binary to /usr/local/bin/monitor-exporter (the one sudo step), writes a per-user LaunchAgent, loads it, and scrapes /metrics once to confirm. Modeled on fancontrol's install.sh. Idempotent; header documents removal. Port/address via MONITOR_EXPORTER_PORT / MONITOR_EXPORTER_ADDRESS.
• Everything in the zip. make-app.sh now stages install-exporter.sh beside monitor-exporter, so ./install-exporter.sh works straight from the unpacked zip. Verified locally — the built zip's top level:

  install-exporter.sh
  monitord
  monitor-exporter
  monitor.app/
  

• Bump to 1.7.0. The exporter is a feature, so it earns a minor. monitor-exporter: native Prometheus /metrics for SMC and GPU (#58) #59 merged with a release:minor label but the auto-bump cut a patch (1.6.3) instead — so this uses release.yml's documented escape hatch (a PR that sets MonitorVersion.string ships exactly that version) to cut v1.7.0 on merge.
• Docs: docs/exporter.md gets the one-command install and a removal recipe; README's download note lists the script.

Verified

swift build && swift test (279 tests) green, lint clean, make-app.sh builds and stages all four artifacts, and the ditto zip contains them at the top level. install-exporter.sh passes bash -n; I did not run it here — it needs your interactive sudo password and installs a persistent LaunchAgent, so it's yours to run (! Scripts/install-exporter.sh).