When a plugin command was dispatched, record_recent was called but
tabs[i].last_cmd was never set. Consequently, pressing Enter or Space on
an empty command line after running a plugin command failed to repeat it.
This records tabs[i].last_cmd on plugin dispatch and requests command-line
focus and dynamic input syncing when an interactive plugin command starts.
- Add LayerConfig struct and add_layer / modify_layer methods to HostApi trait
- Implement IPC request/response serialization for AddLayer and ModifyLayer
- Implement HostSession methods with CAD property defaults and selective modification
- Refresh layer panel UI and invalidate scene layer dependencies upon layer changes
- Add unit tests for add_layer with defaults and partial modify_layer
yztink