Degree-1 junction demand trap (fixed)

A degree-1 JUNCTION carrying a demand used to be silently auto-reclassified to an atmospheric Open Pipe boundary on load, discarding the demand and turning a metered draw-off into a pressure-driven blow-open — a plausible-but-wrong result that produced no error at all. Fixed by modelling end-of-branch draws as Assign Flowrate, which preserves the demand through save/load.

• You're modelling an end-of-branch draw-off point (a single hose bib, a dead-end tap) and want it to keep its assigned flow after a save/reload.
• You're reviewing an older saved model and see a dead-end node behaving as atmospheric-open rather than demanding flow — this is the historical bug the fix addresses, worth checking on legacy files.
• You're adding a new node-classification rule and want the cautionary example for why silent reclassification on load is a dangerous pattern.

Method: classify a degree-1 node with a nonzero demand as Assign Flowrate at model-build time (not Open Pipe), so the graph never contains a state where a demand exists but the node type can't express it.