feat(phase-10): STRUCT-002 export engine core

Task: STRUCT-002
Branch: cline-dev-dishant
Cross-branch notes: none  no shared dependencies with Richard's phase 9/6 work

- ProjectExporter class (pure, filesystem-agnostic)
- Converts legacy project.json to v2 multi-file format
- Outputs: nodegx.project.json, nodegx.routes.json, nodegx.styles.json,
  components/_registry.json, per-component component.json/nodes.json/connections.json
- Helper exports: legacyNameToPath, inferComponentType, flattenNodes, countNodes
- Full legacy type definitions (LegacyProject, LegacyComponent, LegacyNode, etc.)
- 50 unit tests in tests/io/ProjectExporter.test.ts
- Registered in tests/index.ts

packages/noodl-editor/tests/index.ts

@@ -12,3 +12,4 @@ export * from './projectmerger';
 export * from './projectpatcher';
 export * from './utils';
 export * from './schemas';
+export * from './io';