feat: implement debounced autosave with strict LocalStorage garbage collection (Stage 2 Task B)

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

@@ -92,6 +92,20 @@ export async function initEditor(elementId, dotNetHelper, initialMarkdown) {
             }
         });
 
+        // Hook into the Crepe content update listener system with 300ms JS debounce
+        let debounceTimeout = null;
+        crepe.on((listener) => {
+            listener.markdownUpdated((ctx, markdown, prevMarkdown) => {
+                if (debounceTimeout) {
+                    clearTimeout(debounceTimeout);
+                }
+                debounceTimeout = setTimeout(() => {
+                    dotNetHelper.invokeMethodAsync('OnEditorContentChanged', markdown)
+                        .catch(err => console.error("[Milkdown] Failed to notify editor content changed:", err));
+                }, 300);
+            });
+        });
+
         // Store the editor instance in the map
         editorCache.set(elementId, crepe);
 
@@ -131,3 +145,21 @@ export async function destroyEditor(elementId) {
         editorCache.delete(elementId);
     }
 }
+
+/**
+ * Safely retrieves all localStorage keys starting with the "nexus-bkp-" prefix.
+ */
+export function getBackupKeys() {
+    const keys = [];
+    try {
+        for (let i = 0; i < localStorage.length; i++) {
+            const key = localStorage.key(i);
+            if (key && key.startsWith('nexus-bkp-')) {
+                keys.push(key);
+            }
+        }
+    } catch (err) {
+        console.error("[Milkdown] Error listing localStorage keys:", err);
+    }
+    return keys;
+}