Let a Sequence grow an output as you connect the last one

The Outputs setting is gone. A Sequence now keeps one free output below the
last connected one: nothing plugged in is one output, connecting the spare
grows a new one, unplugging the bottom edge shrinks it back.

It counts the last *connected* port rather than the number of edges, so
unplugging a middle one leaves a gap instead of silently dropping an edge.

Removing the setting also removes a bug it caused. Typing in the Outputs field
did nothing and the arrow keys did nothing, while dragging the value worked:
onInput fires per keystroke, the preview writes into node.params, that emits
'project', and Inspector.refreshValues() sees the node's signature change --
the port list is part of it -- so it rebuilds and destroys the row being typed
in. A drag survives because it keeps receiving globalpointermove on the old
widget. refreshValues() has no focus guard where refreshLive() does; the trap
is still there for the next typed field that changes a node's shape.

Ports that depend on the edges around a node mean derivePorts needs the graph,
not just the params, so resolveDef and portSignature take it too. And a node
whose ports are derived cannot know how many it has from its type, so run is
handed the definition resolved for it.

src/core/graph/dropTarget.ts

@@ -12,7 +12,7 @@ export interface PortSide {
 
 export function portTypeOf(graph: Graph, side: PortSide, lookup: BehaviorLookup): PortType | undefined {
   const node = findNode(graph, side.nodeId);
-  const def = node && resolveDef(node, lookup);
+  const def = node && resolveDef(node, graph, lookup);
   const list = side.isOutput ? def?.outputs : def?.inputs;
   return list?.find((p) => p.key === side.port)?.type;
 }
@@ -40,7 +40,7 @@ export function dropTargetPort(
 ): PortSide | null {
   if (nodeId === from.nodeId) return null;
   const node = findNode(graph, nodeId);
-  const def = node && resolveDef(node, lookup);
+  const def = node && resolveDef(node, graph, lookup);
   const fromType = portTypeOf(graph, from, lookup);
   if (!def || fromType === undefined) return null;
   const candidates = compatiblePorts(def, fromType, from.isOutput)