## Compilation fixes
- Fix XAML namespace reference XplorePlane.Converters → XplorePlane.Helpers (EventLogView, StateDisplayView)
- Add missing using for ISampleTypeRepository / JsonSampleTypeRepository in App.xaml.cs
- Fix ILoggerService.Warn() calls using Exception as first arg instead of message string
- Serialize CncProgram to JSON when passing to MatrixLayout (expects string, not CncProgram object)
- Suppress CS8632 nullable annotation warnings project-wide
## BGA wizard fixes
- Fix preview not showing on step 3: force RefreshBgaPreview() when entering final step
- Add step validation in CanNext() to prevent skipping to preview with invalid inputs
- Notify NextCommand.CanExecuteChanged when inputs change
- Fix RunProgress runtime binding error: set Mode=OneWay for ProgressBar.Value
## Operator toolbox: prevent duplicate insertion
- Add static OperatorTarget property for direct dispatch to active pipeline
- PipelineEditorView registers as toolbox target on load (floating window only)
- CNC page sets initial target; PipelineEditorWindow resets to CNC pipeline on close
- '+' button inserts only to the active pipeline instead of broadcasting to all subscribers
## Pipeline editor status bar messages
- Add StatusBarMessageEvent / StatusBarMessagePayload to CommonEvents.cs
- PipelineEditorViewModel publishes status on all ops (add/remove/reorder/save/execute)
- MainViewModel subscribes and displays on main window bottom status bar
- Auto-clear after timeout (3s info, 5s error)
## docs
- Merge three architecture docs into consolidated XplorePlane-架构与结构说明.md
QI Mingxuan