The waiting variant blocked on a fixed progress bar (up to 120s) even
when every start command had already failed (e.g. the uBridge >= 1.2.3
409), burying the error behind two minutes of silence. Drop it: the
single start_gns3_node now sends the commands and returns per-node
results immediately (GNS3StartNodeQuickTool kept as an alias). Boot
waiting moves to a dedicated wait_seconds tool the agent calls
explicitly between start and status checks, with a 600s ceiling and
liveness logging every 5s.
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