v0.7.2: background service (opt-in) and squidbrake explain

Keep it running in the background, if you want to (thanks @bishboi, #63)

• The first time you run squidbrake in a terminal, it asks once whether to keep it running in the background and at every login. Enter means no.
  • macOS uses launchd, Linux a systemd user service, Windows a login entry.
  • squidbrake start --background turns it on without asking. squidbrake service status | stop checks it or takes it out.
  • Agents fail closed, so a closed terminal no longer locks them out.
• Dashboard:
  • Each agent has its own color and initials.
  • Activity opens on Chains: one card per session, with its steps in order. "Show chain" in the approval queue jumps to that session.

squidbrake explain "<command>" (thanks @SaiThihan, #64)

• Shows how Squidbrake reads a shell command, and what the gateway would do with it, without running anything. Exit code 1 when it's more than "other".

$ squidbrake explain "git push origin main"
other
  git push origin main other
  gateway: waits for a person (approve-git-push)

Fixes

• squidbrake service --help shows the service's own help.
• The test suite passes on Windows.

Install this version (0.7.2)

Windows (PowerShell):

$env:SQUIDBRAKE_VERSION="0.7.2"; irm https://pilots.squidbrake.com/install.ps1 | iex

macOS / Linux:

curl -fsSL https://pilots.squidbrake.com/install.sh | SQUIDBRAKE_VERSION=0.7.2 sh

With pip: pip install squidbrake==0.7.2. Docker: docker pull ghcr.io/batrapulkit/squidbrake:0.7.2

Running the line again without SQUIDBRAKE_VERSION goes back to the newest. Every version:
https://github.com/batrapulkit/squidbrake/releases