Enhance chatbot conversation engine and add retrieval eval suite

server.js

@@ -740,6 +740,7 @@ app.get('/api/admin-content', async (_req, res) => {
 const MAX_CHATBOT_ENTRIES = 500
 let chatbotEntries = []
 let chatbotWritePromise = Promise.resolve()
+let chatbotFileMtimeMs = 0
 
 function queueChatbotWrite() {
   chatbotWritePromise = chatbotWritePromise
@@ -756,25 +757,43 @@ function queueChatbotWrite() {
     })
 }
 
-function loadChatbotFromDisk() {
-  return readFile(CHATBOT_FILE, 'utf8')
-    .then(raw => {
-      const parsed = JSON.parse(raw)
-      chatbotEntries = Array.isArray(parsed) ? parsed.slice(0, MAX_CHATBOT_ENTRIES) : []
-    })
-    .catch(() => {
-      chatbotEntries = []
-    })
+async function loadChatbotFromDisk() {
+  try {
+    const [fileStats, raw] = await Promise.all([
+      stat(CHATBOT_FILE),
+      readFile(CHATBOT_FILE, 'utf8'),
+    ])
+    const parsed = JSON.parse(raw)
+    chatbotEntries = Array.isArray(parsed) ? parsed.slice(0, MAX_CHATBOT_ENTRIES) : []
+    chatbotFileMtimeMs = fileStats.mtimeMs
+  } catch {
+    chatbotEntries = []
+    chatbotFileMtimeMs = 0
+  }
+}
+
+async function refreshChatbotFromDiskIfChanged() {
+  try {
+    const fileStats = await stat(CHATBOT_FILE)
+    if (fileStats.mtimeMs <= chatbotFileMtimeMs) return
+    await loadChatbotFromDisk()
+  } catch {
+    if (chatbotFileMtimeMs === 0) return
+    chatbotEntries = []
+    chatbotFileMtimeMs = 0
+  }
 }
 
 // Public: return all chatbot entries for client-side matching
-app.get('/api/chatbot-content', (req, res) => {
+app.get('/api/chatbot-content', async (req, res) => {
+  await refreshChatbotFromDiskIfChanged()
   res.json(chatbotEntries)
 })
 
 // Admin: get all entries
-app.get('/api/admin/chatbot-content', (req, res) => {
+app.get('/api/admin/chatbot-content', async (req, res) => {
   if (!isValidAdminSession(req)) { res.status(401).json({ message: 'Not authenticated.' }); return }
+  await refreshChatbotFromDiskIfChanged()
   res.json(chatbotEntries)
 })