A fourth Rule kind: overflow = max(0, factor × (level − threshold)). It stays
shut until its `+` level passes its `−` threshold, so an outflow on it spills only
the excess — a spillway / hard ceiling the smooth rules can't draw.
Gap can't stand in for it: it's signed and bidirectional (coffee cooling relies on
that), so below the threshold a gap outflow runs backwards. Clamping at zero is the
whole point, and it can't be applied globally without breaking gap. This is the
additive vocabulary growth ADR-0004 anticipates — a new kind in the union plus a
case in the evaluator — alongside touch-ups to the rule validator and the inspector.
A free-text "why this element is here" note on Stocks, Flows,
Converters, and Information Links — editable in the Inspector next to
the unit, shown read-only in the gloss card below the generic kind
definition on selection. The Inspector now also opens for Information
Links, which previously had no editing surface.
A Stock can carry a display unit (°C, people, $, …): a new optional field, an
inspector text input, validation + round-trip in io, and a readout beside the
live value on the canvas. Equip the demonstrative samples (Water L, Balance $,
Coffee °C, Population/Epidemic people, Yeast cells). Also bumps the fill gauge
opacity for a more vivid level.
- ResultsPanel: a Simulate panel that charts every Stock over time (hand-built
SVG), with start/stop/dt run controls and a divergence warning
- Inspector: edit a selected Stock's initial value or a Flow/Converter's rule
- store: undoable setInitialValue / setRule / setSimSpec actions
