fix: add stable keys and lifecycle methods to message tracking action

- Add unique IDs to ConversationContent for stable Svelte keying
- Implement update/destroy lifecycle methods in trackingAction
- Reset chat area when clearing conversation to prevent stale references

Components/ChatArea.svelte

@@ -151,6 +151,18 @@
 
   function trackingAction(element: HTMLElement, { index, role }: { index: number, role: Role }) {
     messageElements.push({ index: index, element: element, role: role });
+    return {
+      update({ index, role }: { index: number, role: Role }) {
+        const entry = messageElements.find((message) => message.element === element);
+        if (entry) {
+          entry.index = index;
+          entry.role = role;
+        }
+      },
+      destroy() {
+        messageElements = messageElements.filter((message) => message.element !== element);
+      }
+    };
   }
 
   $: if (scrollToBottomButton) {
@@ -169,7 +181,7 @@
     <div class="top-fade"></div>
   {/if}
   <div class="chat-area" bind:this={chatContainer} on:scroll={updateScrolledState}>
-    {#each messages as message, index}
+    {#each messages as message, index (message.id)}
       {@const content = message.getDisplayContent()}
       {#if message.shouldDisplayContent && content.trim() !== ""}
         {#if message.role === Role.User}

Components/ChatWindow.svelte

@@ -177,6 +177,8 @@
     isSubmitting = false;
     currentThought = null;
 
+    chatArea?.resetChatArea();
+
     chatService.onNameChanged?.("");
     conversationStore.clearResetFlag();
   }

Conversations/ConversationContent.ts

@@ -20,6 +20,10 @@ type ConversationContentInit = {
 };
 
 export class ConversationContent {
+    // Runtime-only counter for Svelte {#each} keying
+    private static nextId: number = 0;
+
+    public readonly id: number;
     public role: Role;
     public timestamp: Date;
     public content: string | undefined;
@@ -51,6 +55,7 @@ export class ConversationContent {
      * @param init.errorType - Indicates that this contains an error of the given type
      */
     constructor(init: ConversationContentInit) {
+        this.id = ConversationContent.nextId++;
         this.role = init.role;
         this.timestamp = init.timestamp ?? new Date();
         this.content = init.content;