runRootCommand called discoverAuthStorage without a try/catch, so a
configured-but-unreachable broker with no cached snapshot re-threw
AuthBrokerError as a raw uncaught exception at startup, unlike the other
startup paths that print a clean stderr message and exit non-zero.
Wrap the startup auth discovery: broker failures now report an actionable
message naming the broker URL and the recovery options (start it with
`omp auth-broker serve`, or reset `auth.broker.url`/`auth.broker.token`)
and exit 1. Unrelated errors still propagate. The broker still replaces
the local store when configured; no silent fallback to local credentials.
Fixes#8096
roboomp
a67da14e4e