fix(chat): Keep 1 history entry per session

chat.html

@@ -335,6 +335,7 @@
                 isBusy: false,
                 abortController: null,
                 userHasScrolledUp: false,
+                sessionId: null,
 
                 models: [
                     { name: "gpt-4.1", chat: chatWithOpenAI, key: "OPENAI_API_KEY" },
@@ -344,6 +345,7 @@
                 ],
 
                 async init() {
+                    this.sessionId = +new Date();
                     this.historyItems = loadHistory();
                     setTimeout(() => this.$refs.promptInput.focus(), 0);
                 },
@@ -370,7 +372,7 @@
 
                 handleScroll() {
                     const el = this.$refs.msgBox;
-                    this.userHasScrolledUp = el.scrollHeight - el.clientHeight - el.scrollTop > 50;
+                    this.userHasScrolledUp = el.scrollHeight - el.clientHeight - el.scrollTop > 100;
                 },
 
                 scrollToBottom() {
@@ -442,7 +444,7 @@
                     } finally {
                         this.isBusy = false;
                         this.abortController = null;
-                        this.historyItems = saveHistory([...this.messages]);
+                        updateSessionHistory(this.sessionId, this.messages);
                     }
                 },
 
@@ -638,6 +640,7 @@
 
             const STORAGE_KEY = "chat_conversations";
             const todayKey = () => new Date().toISOString().slice(0, 10);
+
             const loadHistory = () => {
                 try {
                     return JSON.parse(localStorage.getItem(STORAGE_KEY) || "{}")[todayKey()] || [];
@@ -645,11 +648,19 @@
                     return [];
                 }
             };
-            const saveHistory = (messages) => {
+
+            const updateSessionHistory = (sessionId, messages) => {
                 const all = JSON.parse(localStorage.getItem(STORAGE_KEY) || "{}");
                 const today = todayKey();
                 all[today] ??= [];
-                all[today].unshift({ time: new Date().toISOString(), messages });
+
+                const idx = all[today].findIndex((item) => item.sessionId === sessionId);
+                if (idx >= 0) {
+                    all[today][idx] = { sessionId, time: all[today][idx].time, messages };
+                } else {
+                    all[today].unshift({ sessionId, time: new Date().toISOString(), messages });
+                }
+
                 all[today] = all[today].slice(0, 5);
                 localStorage.setItem(STORAGE_KEY, JSON.stringify(all));
                 return all[today];