a setup script that doesn't ruin your entire machine.
setting up a new laptop or cloud instance is one of the most frustrating experiences in software.
you spend half a day remembering which packages were installed via brew, which came from apt, why your zshrc has missing aliases, and why your SSH agent isn't talking to GitHub.
most public dotfile scripts make two fatal mistakes:
1. they assume you're on standard Ubuntu and choke when run on macOS or Arch.
2. they blindly run cp or ln -sf, quietly overwriting custom configurations you wrote three months ago.
the rules of agent-setup
1. Strict Idempotency: you can run agent-setup once or fifty times in a row. if a tool or link is already correctly configured, it leaves it alone.
2. Pre-flight Environment Inspection: before creating a symlink or triggering an install, the script verifies the platform, detects existing package managers, and checks write permissions.
3. Zero Third-Party Dependencies: pure POSIX-compliant Bash. no Python dependencies, no Node runtime requirements, no Docker bootstrap needed just to run the installer.