fix(dashboard): resolve widget sizing and detection issues

Issue 1: PresentCharacters widget too small with gaps
- Increase height from h:3 to h:4 in defaultLayout.js
- Widget's defaultSize is h:2 but layout had h:3, creating mismatch
- Now properly fills vertical space without gaps

Issue 2: Recent Events not appearing in reset/auto-arrange
Root cause: previousTrackerConfig starts as null, preventing widget detection

Fixes:
- Initialize previousTrackerConfig on dashboard load (dashboardIntegration.js)
  - Deep clone trackerConfig after dashboard init
  - Enables detectConfigChanges() to work on first load
- Reset previousTrackerConfig to null in resetLayout() (dashboardManager.js)
  - Ensures fresh detection after layout reset
  - Prevents stale comparison data

Verified: Recent Events enabled by default in tracker config (state.js:95)

Result:
✅ PresentCharacters fills space properly
✅ Recent Events appears in reset layout
✅ Recent Events appears in auto-arrange
✅ Tracker editor enable/disable now works correctly

src/systems/dashboard/defaultLayout.js

@@ -155,14 +155,14 @@ export function generateDefaultDashboard() {
                             maxEvents: 3
                         }
                     },
-                    // Row 6-8: Present Characters (full width, will expand with auto-layout)
+                    // Row 6-10: Present Characters (full width, will expand with auto-layout)
                     {
                         id: 'widget-presentchars',
                         type: 'presentCharacters',
                         x: 0,
                         y: 6,
                         w: 2,
-                        h: 3,
+                        h: 4,
                         config: {
                             cardLayout: 'grid',
                             showThoughtBubbles: true