fix: resolve incorrect link activation for first and last sections (#869)

Author: Vardhaman619

apps/svelte.dev/src/routes/docs/[...path]/OnThisPage.svelte

@@ -10,25 +10,33 @@
 	afterNavigate(() => {
 		current = location.hash.slice(1);
 		headings = content.querySelectorAll('h2');
+		update(); // Ensure active link is set correctly on navigation
 	});
 
+	// Update function to activate the correct section link
 	function update() {
-		// a section is 'active' when it crosses the threshold
 		const threshold = (innerHeight * 1) / 3;
+		let found = false;
 
-		for (let i = 0; i < headings.length; i += 1) {
+		for (let i = 0; i < headings.length; i++) {
 			const heading = headings[i];
 			const next = headings[i + 1];
 
+			// If the current heading is above the threshold and the next heading is below it
 			if (
-				next &&
 				heading.getBoundingClientRect().top < threshold &&
-				next.getBoundingClientRect().top > threshold
+				(!next || next.getBoundingClientRect().top > threshold)
 			) {
 				current = heading.id;
+				found = true;
 				break;
 			}
 		}
+
+		// Handle case when scrolled to the top of the page
+		if (!found && scrollY === 0) {
+			current = '';
+		}
 	}
 </script>