Design plugin system API

[Konstantysz]

Goal

Define stable C++ API for external node plugins (.dll/.so libraries).

Requirements

• Plugin discovery from external/plugins/ directory
• Manifest file (plugin.json) with metadata (name, version, nodes)
• Interface: INodePlugin with CreateNode(type) -> std::unique_ptr<Node>
• Dynamic loading via dlopen (Linux) or LoadLibrary (Windows)
• Sandboxing: Plugins run in separate process or with restricted permissions

Deliverable

Design document (not full implementation):

• API interface headers
• Example plugin template
• Loading mechanism pseudocode

Next Steps

Separate issues for implementation, UI, example plugins.