Developers currently start the API server and Vite frontend by hand with fixed ports. This script keeps that workflow fast while avoiding bind failures when a previous run or another service already owns one of the defaults.
Constraint: Web UI must receive the actual backend URL whenever the backend port changes
Rejected: Reuse Vite auto-port behavior alone | it would not check or report the backend port and could leave the browser pointed at 3456
Confidence: high
Scope-risk: narrow
Directive: Keep this script dependency-light so it remains usable on a default macOS developer machine
Tested: bash -n scripts/start-web-ui.sh
Tested: ./scripts/start-web-ui.sh --help
Tested: occupied preferred ports 45678 and 45679, script switched to 45680 and 45681 and reached Web UI ready
Not-tested: full bun run verify, script-only developer workflow change
