refactor: remove unnecessary header-hidden and footer-hidden attributes

Empty flex containers with no padding or min-height naturally collapse to zero height,
making the visibility management logic unnecessary.

Author: Artur-

packages/grid/src/styles/vaadin-grid-base-styles.js

@@ -80,11 +80,6 @@ export const gridStyles = css`
     box-sizing: border-box;
   }
 
-  :host([header-hidden]) [part='header'],
-  :host([footer-hidden]) [part='footer'] {
-    display: none;
-  }
-
   #items {
     flex-grow: 1;
     flex-shrink: 0;

packages/grid/src/vaadin-grid.js

@@ -278,32 +278,6 @@ class Grid extends GridMixin(ElementMixin(ThemableMixin(PolylitMixin(LumoInjecti
     return gridStyles;
   }
 
-  /** @protected */
-  firstUpdated() {
-    super.firstUpdated();
-
-    // Handle header slot visibility
-    const headerSlot = this.shadowRoot.querySelector('slot[name="header"]');
-    const footerSlot = this.shadowRoot.querySelector('slot[name="footer"]');
-
-    const updateSlotVisibility = () => {
-      // Check header slot
-      const hasHeaderContent = headerSlot.assignedNodes().length > 0;
-      this.toggleAttribute('header-hidden', !hasHeaderContent);
-
-      // Check footer slot
-      const hasFooterContent = footerSlot.assignedNodes().length > 0;
-      this.toggleAttribute('footer-hidden', !hasFooterContent);
-    };
-
-    // Initial check
-    updateSlotVisibility();
-
-    // Listen for slot changes
-    headerSlot.addEventListener('slotchange', updateSlotVisibility);
-    footerSlot.addEventListener('slotchange', updateSlotVisibility);
-  }
-
   /** @protected */
   render() {
     return html`

packages/grid/test/grid-slots.test.js

@@ -52,10 +52,10 @@ describe('grid slots', () => {
       expect(headerRect.bottom).to.be.at.most(tableRect.top + 1);
     });
 
-    it('should hide empty header slot', () => {
+    it('should have zero height when header slot is empty', () => {
       const headerPart = grid.shadowRoot.querySelector('[part="header"]');
-      const computedStyle = window.getComputedStyle(headerPart);
-      expect(computedStyle.display).to.equal('none');
+      const rect = headerPart.getBoundingClientRect();
+      expect(rect.height).to.equal(0);
     });
 
     it('should show header slot with content', async () => {
@@ -127,10 +127,10 @@ describe('grid slots', () => {
       expect(footerRect.top).to.be.at.least(tableRect.bottom - 1);
     });
 
-    it('should hide empty footer slot', () => {
+    it('should have zero height when footer slot is empty', () => {
       const footerPart = grid.shadowRoot.querySelector('[part="footer"]');
-      const computedStyle = window.getComputedStyle(footerPart);
-      expect(computedStyle.display).to.equal('none');
+      const rect = footerPart.getBoundingClientRect();
+      expect(rect.height).to.equal(0);
     });
 
     it('should show footer slot with content', async () => {