Implement Phase 14 - Overlay, Operational, and Display Widget Component Migration (#135)

* Implement Phase 14.1 - Overlay Widget Component Tests

Add regression tests for overlay widgets to verify they preserve
identity, styling, slots, and event semantics through the widget
component architecture.

**Overlay Widgets Tested (33 tests):**
- OverlaySurface: component boundary, overlay slots, dismissible mode, background fill
- Dialog: component boundary, open state, modal mode, size variants, actions slot
- AlertDialog: component boundary, severity levels, confirmation requirement
- ContextMenu: component boundary, open state, placement options, anchor positioning, active item tracking
- Toast: component boundary, open state, placement options, duration configuration, severity levels

**Test Coverage:**
- Widget identity preservation across renders and modes
- Event semantics (click) for context_menu
- Bounded local state support for overlay lifecycle
- Overlay lifecycle behavior (modes, background fill)

* Implement Phase 14.2 - Operational Widget Component Tests

Add regression tests for operational widgets to verify they preserve
identity, styling, slots, and event semantics through the widget
component architecture.

**Operational Widgets Tested (25 tests):**
- StreamWidget: component boundary, ordering modes, entry severity levels
- ProcessMonitor: component boundary, process entries, state display
- SupervisionTreeViewer: component boundary, nested children, expanded state, node status
- ClusterDashboard: component boundary, node status, summary information

**Test Coverage:**
- Widget identity preservation across renders and modes
- Event semantics (change) for all operational widgets
- Bounded local state support for operational state
- Real-time update support for streams and monitoring

* Implement Phase 14.3 - Display System Widget Component Tests

Add regression tests for display system widgets to verify they preserve
identity, styling, slots, and event semantics through the widget
component architecture.

**Display System Widgets Tested (32 tests):**
- Viewport: component boundary, axis configuration, offset positioning, clip mode, scrollbar configuration
- ScrollBar: component boundary, orientation, position tracking, viewport reference, sync groups
- SplitPane: component boundary, direction, ratio configuration, resizable mode, slot rendering
- Canvas: component boundary, dimensions, unit configuration, background options, drawing operations, clip mode

**Test Coverage:**
- Widget identity preservation across renders and modes
- Event semantics (change) for scroll_bar and canvas
- Bounded local state support for display interactions
- Display system interaction support (independent scroll, sync groups, size constraints)

* Implement Phase 14.4 - Integration Tests

Add end-to-end integration tests for Phase 14 widget migrations.
Verifies that overlay, operational, and display widgets work correctly
together in realistic screen scenarios.

**Test Scenarios:**
- Overlay widget integration with dialog, toast, and container
- Operational widget integration with status, stream, and process monitor
- Display system widget integration with viewport
- Widget identity preservation across renders and modes (overlay, operational, display)
- Bounded local state support for all widget families

**Total Phase 14 Tests:**
- Phase 14.1: 33 overlay widget tests
- Phase 14.2: 25 operational widget tests
- Phase 14.3: 32 display system widget tests
- Phase 14.4: 9 integration tests
- **Total: 99 regression tests**

Author: pcharbon70