Add Get/Set properties nodes and a breadcrumb for opened sub-behaviors

Get properties / Set properties work like their variable counterparts:
one port per chosen property, an unconnected input writes its inline
value. A port chosen from the built-in list keeps that property's field
and default (height starts at 100, color is a colour field). "object" is
reserved for the fixed input, checked by the command and on load.

The property picker names the owning type ("Sprite width"), and text
fields can now carry a suggestion list; Get/Set property use it.

Double-clicking a call node shows the path of opened behaviors under the
graph header. Clicking an entry jumps back and trims the path; choosing
a behavior any other way hides it. Reopening a behavior already on the
path steps back to it instead of repeating it. The bar shows before the
graph switches, otherwise it clips the graph that was just fitted.

The "Add node..." header button is gone; nodes come from the context menu.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/graph/nested.ts

@@ -9,6 +9,8 @@ export const BEHAVIOR_END = 'BehaviorEnd';
 export const RUN_BEHAVIOR = 'RunBehavior';
 export const GET_VARIABLES = 'GetVariables';
 export const SET_VARIABLES = 'SetVariables';
+export const GET_PROPERTIES = 'GetProperties';
+export const SET_PROPERTIES = 'SetProperties';
 
 export const BEHAVIOR_PARAM = 'behavior';
 
@@ -21,11 +23,21 @@ export function declaresVariablePorts(type: string): boolean {
   return type === GET_VARIABLES || type === SET_VARIABLES;
 }
 
+/** Nodes whose declared ports are properties of the object they are handed. */
+export function declaresPropertyPorts(type: string): boolean {
+  return type === GET_PROPERTIES || type === SET_PROPERTIES;
+}
+
 /** Identifier-like, and not `exec`: that key belongs to the fixed flow port of every terminal node. */
 export function isValidPortName(name: string): boolean {
   return isValidFieldName(name) && name !== 'exec';
 }
 
+/** Keys a declared port cannot take: the node's fixed ports on the side it declares (`object`). */
+export function fixedPortKeys(def: NodeDef): string[] {
+  return (def.declaresPorts === 'inputs' ? def.inputs : def.outputs).map((p) => p.key);
+}
+
 /** The single start (or end) node of a graph; a second one is ignored. */
 export function terminalNode(graph: Graph, type: string): GraphNode | undefined {
   return graph.nodes.find((n) => n.type === type);
@@ -56,7 +68,7 @@ export function declaredPorts(graph: Graph | undefined, type: string): PortDef[]
 export function resolveDef(node: GraphNode, graph: Graph, lookup: BehaviorLookup): NodeDef | undefined {
   const def = nodeDef(node.type);
   if (!def || (!def.declaresPorts && !def.derivePorts)) return def;
-  const own = def.declaresPorts ? (node.ports ?? []).map(portDefOf) : [];
+  const own = def.declaresPorts ? (node.ports ?? []).map((p) => (def.declaredPort ?? portDefOf)(p)) : [];
   const side = (which: 'inputs' | 'outputs') => (def.declaresPorts === which ? own : []);
   const grown = def.derivePorts?.({ node, graph, behaviors: lookup }) ?? {};
   return {