feat: implement dynamic knowledge graph updates and state management services

src/NexusReader.UI.Shared/wwwroot/js/readerObserver.js

@@ -0,0 +1,22 @@
+export function initObserver(dotNetHelper, containerSelector, itemSelector) {
+    const options = {
+        root: null,
+        rootMargin: '0px',
+        threshold: 0.6 // 60% of the block must be visible
+    };
+
+    const observer = new IntersectionObserver((entries) => {
+        entries.forEach(entry => {
+            if (entry.isIntersecting) {
+                const id = entry.target.id;
+                const content = entry.target.innerText;
+                dotNetHelper.invokeMethodAsync('HandleBlockReached', id, content);
+            }
+        });
+    }, options);
+
+    const items = document.querySelectorAll(itemSelector);
+    items.forEach(item => observer.observe(item));
+
+    return observer;
+}