Replace React Router loader/action state paths with SWR query and mutation hooks.
Add targeted run and board EventSource managers that invalidate SWR keys, and refresh embedded SPA assets.
Implement the web-first install experience across the server, CLI, API spec,
web app, and packaged SPA assets.
This also removes test-side process env mutation by pushing env-dependent
decision points behind explicit helpers and test wiring.
Replace the old React Router SSR setup with a static SPA build served by
fabro-server, move setup and GitHub auth handling into Rust, and update the
default local web URL and stale Arc-era references to match the Fabro name.
