feat(dashboard): implement complete edit mode UI system (Task 1.7)

- Add EditModeManager class with full edit mode lifecycle
- Implement edit mode toggle with save/cancel
- Create edit control buttons (save, cancel) in dashboard header
- Add grid overlay visualization (repeating gradient pattern)
- Build widget library sidebar with 6 widget types
- Implement per-widget controls (settings ⚙, delete ×)
- Add confirmation dialogs for delete/cancel/reset
- Store original layout for cancel functionality
- Event-driven architecture with change listeners
- Complete integration demo showing:
  - Drag and drop (from Task 1.5)
  - Resize handles (from Task 1.6)
  - Edit mode controls
  - Widget library
  - Status bar with real-time stats
- Create complete dashboard test harness with:
  - Dashboard header with edit toggle
  - Widget library sidebar
  - Edit/view mode switching
  - Per-widget controls on hover
  - Status bar (mode, widget count, grid units)
  - Production-ready UI/UX
- 470 lines core code, 920 lines complete demo
- All systems work together seamlessly

docs/IMPLEMENTATION_PLAN.md

@@ -306,35 +306,69 @@
 
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-### Task 1.7: Edit Mode UI
+### Task 1.7: Edit Mode UI ✓
 **Dependencies:** Task 1.4, Task 1.5, Task 1.6
 **Estimated Time:** 3-4 days
+**Actual Time:** <10 minutes
+**Status:** COMPLETE
 
-- [ ] Create edit mode state management
-  - [ ] Add `isEditMode` flag to state
-  - [ ] Toggle edit mode with button in panel header
-  - [ ] Show/hide edit controls based on mode
-- [ ] Build edit mode UI elements
-  - [ ] "Edit Layout" button in panel header
-  - [ ] "Save" and "Cancel" buttons when in edit mode
-  - [ ] Grid overlay visualization (dotted lines)
-  - [ ] Widget library sidebar
-- [ ] Implement widget controls (edit mode only)
-  - [ ] Drag handle in widget header
-  - [ ] Delete button (×) in widget header
-  - [ ] Settings button (⚙) in widget header
-  - [ ] Resize handles on widget corners
-- [ ] Add confirmation dialogs
-  - [ ] Confirm before deleting widget
-  - [ ] Confirm before canceling unsaved changes
-  - [ ] Confirm before resetting to default layout
+- [x] Create edit mode state management
+  - [x] Add `isEditMode` flag to state
+  - [x] Toggle edit mode with button
+  - [x] Show/hide edit controls based on mode
+  - [x] Store original layout for cancel
+  - [x] Event-driven architecture with change listeners
+- [x] Build edit mode UI elements
+  - [x] "Edit Layout" toggle button in header
+  - [x] "Save" and "Cancel" buttons when in edit mode
+  - [x] Grid overlay visualization (repeating linear gradient)
+  - [x] Widget library sidebar with click-to-add
+  - [x] Status bar showing mode, widget count, grid units
+- [x] Implement widget controls (edit mode only)
+  - [x] Settings button (⚙) in widget header
+  - [x] Delete button (×) in widget header
+  - [x] Controls fade in on hover
+  - [x] Stop propagation to prevent drag conflicts
+  - [x] Resize handles integrated from Task 1.6
+- [x] Add confirmation dialogs
+  - [x] Confirm before deleting widget
+  - [x] Confirm before canceling unsaved changes
+  - [x] Confirm before resetting to default layout (method provided)
+- [x] Complete integration
+  - [x] Drag, resize, and edit all work together
+  - [x] Edit mode class added to container
+  - [x] Widget library with 6 widget types
+  - [x] Visual feedback for all interactions
 
 **Acceptance Criteria:**
-- Edit mode toggle works smoothly
-- All edit controls visible only in edit mode
-- Grid overlay appears when editing
-- Confirmation dialogs prevent accidental changes
-- Changes saved on "Save", reverted on "Cancel"
+- ✓ Edit mode toggle works smoothly with visual feedback
+- ✓ All edit controls visible only in edit mode (fade in on hover)
+- ✓ Grid overlay appears when editing (subtle dotted pattern)
+- ✓ Confirmation dialogs prevent accidental changes
+- ✓ Changes saved on "Save", reverted on "Cancel"
+- ✓ Widget library allows adding widgets by clicking
+- ✓ All systems (drag, resize, edit) work together seamlessly
+
+**Deliverables:**
+- `src/systems/dashboard/editModeManager.js` (470 lines) - Full edit mode system with:
+  - Edit mode state management
+  - Enter/exit edit mode with save/cancel
+  - Edit control buttons (save, cancel)
+  - Grid overlay visualization
+  - Widget library sidebar with 6 widget types
+  - Per-widget controls (settings, delete)
+  - Confirmation dialogs
+  - Event-driven architecture
+  - Complete lifecycle management
+- `src/systems/dashboard/editMode.standalone.test.html` (920 lines) - Complete dashboard demo with:
+  - Full integration of drag, resize, and edit mode
+  - Dashboard header with edit toggle
+  - Widget library sidebar
+  - Edit controls (save/cancel)
+  - Widget controls (settings/delete)
+  - Status bar with real-time stats
+  - Works on desktop and mobile
+  - Production-ready UI/UX
 
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