fix: handle Tab navigation from grid in overlay with focus-trap

When grid is inside an overlay with focus-trap, Tab from grid cells now correctly
moves focus to the next element in the overlay by temporarily removing focusexit
from the Tab order. This allows natural Tab flow to work in both regular grid
scenarios (with footer content) and overlay scenarios.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: Artur-

packages/grid/src/vaadin-grid-keyboard-navigation-mixin.js

@@ -715,10 +715,19 @@ export const KeyboardNavigationMixin = (superClass) =>
         return;
       }
 
-      // When Tab (forward) would go to focusexit, let the natural Tab order work instead
-      // This allows tabbing to footer slot content that's outside the scroller
+      // When Tab (forward) would go to focusexit, skip the grid's Tab handling entirely
+      // to allow natural Tab order to work for footer content or overlay scenarios
       if (focusTarget === this.$.focusexit && !e.shiftKey) {
+        // Prevent focus-trap logic from intercepting the event.
+        e.stopPropagation();
         this.toggleAttribute('navigating', true);
+        // Remove focusexit from Tab order before the browser processes Tab
+        this.$.focusexit.tabIndex = -1;
+        // Restore it after the current event completes
+        setTimeout(() => {
+          this.$.focusexit.tabIndex = 0;
+        }, 0);
+        // Don't prevent default and don't focus anything - let browser handle Tab naturally
         return;
       }