Capabilities
Node properties are keyed by capability and property IDs. Common capabilities:
| Capability | Role |
|---|---|
| Layout | Flex direction, width, height, grow |
| Fill | Background color |
| Pointer handler | Press / release callbacks |
| Viewport | Masonry app surface or GPU canvas |
Import constants from koba_wasi_sdk::caps. Full list: koba_wasi_sdk constants.