The daemon's Up RPC previously always blocked in waitForUp (up to 50s)
until the engine connected. The UI does not need this — status updates
already flow through the SubscribeStatus stream.
Add bool async = 4 to UpRequest. When true the daemon starts
connectWithRetryRuns and returns immediately; the CLI path (async=false,
the default) is unchanged.
ProfileSwitcher.SwitchActive now sets Async:true so all three RPCs
(Status, Switch, Down, Up) return quickly. The background goroutine and
its associated race condition are removed entirely.
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