#3474 install.ps1 closes the user's PowerShell window on failure when run via irm | iex

The documented Windows install is irm https://swamp-club.com/install.ps1 | iex. Under iex the script runs inside the caller's own PowerShell session, and scripts/install.ps1 ends its failure paths with exit 1 (unsupported architecture, and the catch-all after 'Installation failed'), plus exit 0 for -Help. exit in an iex'd script exits the user's session, so the window closes and the error message and Discord help line vanish with it.

Expected: a failed install prints the error and leaves the session open.

Fix: replace exit 1 with throw (or return from Main after writing the error), and avoid leaking $ErrorActionPreference = 'Stop' into the caller's session (wrap the body in a scriptblock or function scope). -Help relies on $PSCommandPath, which is empty under iex.

swamp-club now advertises this command on every install CTA (swamp-club#3471), so this should land first.