feat(evaluator): add const/string and const/boolean definitions

Adds native string and boolean constant nodes to coreDefinitions so they
always appear in the flow graph sidebar palette with correct icons:
- string: icon='type' (FiType)
- boolean: icon='toggle' (FiToggleLeft)

Previously these only existed in MOCK_FUNCTIONS and would disappear
when real platform functions loaded from the database.

Author: pyramation

packages/fbp-evaluator/src/definitions/core.ts

@@ -220,7 +220,35 @@ export const stringConcatDef: NodeDefinitionWithImpl = {
   }
 };
 
+export const constStringDef: NodeDefinitionWithImpl = {
+  context: 'js',
+  name: 'string',
+  category: 'const',
+  icon: 'type',
+  outputs: [{ name: 'value', type: 'string' }],
+  props: [{ name: 'value', type: 'string', default: '' }],
+  description: 'Outputs a constant string value',
+  impl: (_inputs, props) => ({
+    value: props.value ?? ''
+  })
+};
+
+export const constBooleanDef: NodeDefinitionWithImpl = {
+  context: 'js',
+  name: 'boolean',
+  category: 'const',
+  icon: 'toggle',
+  outputs: [{ name: 'value', type: 'boolean' }],
+  props: [{ name: 'value', type: 'boolean', default: false }],
+  description: 'Outputs a constant boolean value',
+  impl: (_inputs, props) => ({
+    value: props.value ?? false
+  })
+};
+
 export const coreDefinitions: NodeDefinitionWithImpl[] = [
+  constStringDef,
+  constBooleanDef,
   jsonSelectDef,
   jsonObjectDef,
   flowGuardDef,

packages/fbp-evaluator/src/index.ts

@@ -4,5 +4,5 @@ export type { NodeImplFn, NodeDefinitionWithImpl, EvaluateOptions, PropDefinitio
 // Re-export node definitions for convenience
 export { mathDefinitions, constNumberDef, addDef, multiplyDef } from './definitions/math';
 export { uiDefinitions, pageDef, formDef, inputDef, buttonDef, textDef, graphInputDef, graphOutputDef, graphPropDef } from './definitions/ui';
-export { coreDefinitions, jsonSelectDef, jsonObjectDef, flowGuardDef, stringTemplateDef, stringConcatDef } from './definitions/core';
+export { coreDefinitions, constStringDef, constBooleanDef, jsonSelectDef, jsonObjectDef, flowGuardDef, stringTemplateDef, stringConcatDef } from './definitions/core';
 export { netDefinitions, graphqlRequestDef } from './definitions/net';