Removes header height animation setup

Eliminates manual DOM manipulation for temporary header height adjustment during slide-in animations. This is no longer necessary.

src/renderers/NavigationRenderer.ts

@@ -137,19 +137,6 @@ export class NavigationRenderer {
       </swp-scrollable-content>
     `;
 
-    // Set header to base height for slide-in animation - will be reset after animation completes
-    const header = newGrid.querySelector('swp-calendar-header') as HTMLElement;
-    if (header) {
-        // Get base header height (without all-day rows)
-        const root = document.documentElement;
-        const baseHeaderHeight = getComputedStyle(root).getPropertyValue('--header-height');
-        header.style.height = baseHeaderHeight;
-        console.log('🔄 NavigationRenderer: Set header height to base height for slide-in', {
-            baseHeaderHeight,
-            weekStart: weekStart.toISOString()
-        });
-    }
-
     // Position new grid - NO transform here, let Animation API handle it
     newGrid.style.position = 'absolute';
     newGrid.style.top = '0';