feat: persist scroll position per conversation tab

- Added scrollPosition to Conversation interface
- Save scroll position when switching away from a tab
- Restore exact scroll position when switching back
- Uses -1 to indicate auto-scroll mode (scroll to bottom)
- Prevents interference between scroll restore and auto-scroll

src/lib/components/Terminal.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { claudeStore, type TerminalLine } from "$lib/stores/claude";
-  import { afterUpdate } from "svelte";
+  import { afterUpdate, tick } from "svelte";
   import ConversationTabs from "./ConversationTabs.svelte";
   import Markdown from "./Markdown.svelte";
   import HighlightedText from "./HighlightedText.svelte";
@@ -10,6 +10,8 @@
   let shouldAutoScroll = true;
   let lines: TerminalLine[] = [];
   let currentSearchQuery = "";
+  let currentConversationId: string | null = null;
+  let isRestoringScroll = false;
 
   searchQuery.subscribe((value) => {
     currentSearchQuery = value;
@@ -19,14 +21,46 @@
     lines = value;
   });
 
+  claudeStore.activeConversationId.subscribe(async (newId) => {
+    if (!newId) return;
+
+    // Save current conversation's scroll position before switching
+    if (currentConversationId && currentConversationId !== newId && terminalElement) {
+      const position = shouldAutoScroll ? -1 : terminalElement.scrollTop;
+      claudeStore.saveScrollPosition(currentConversationId, position);
+    }
+
+    currentConversationId = newId;
+
+    // Restore scroll position for the new conversation after DOM updates
+    await tick();
+    if (terminalElement) {
+      const savedPosition = claudeStore.getScrollPosition(newId);
+      isRestoringScroll = true;
+      if (savedPosition === -1) {
+        // Auto-scroll to bottom
+        shouldAutoScroll = true;
+        terminalElement.scrollTop = terminalElement.scrollHeight;
+      } else {
+        // Restore to saved position
+        shouldAutoScroll = false;
+        terminalElement.scrollTop = savedPosition;
+      }
+      // Small delay to prevent the scroll handler from overriding our restore
+      setTimeout(() => {
+        isRestoringScroll = false;
+      }, 50);
+    }
+  });
+
   function handleScroll() {
-    if (!terminalElement) return;
+    if (!terminalElement || isRestoringScroll) return;
     const { scrollTop, scrollHeight, clientHeight } = terminalElement;
     shouldAutoScroll = scrollHeight - scrollTop - clientHeight < 100;
   }
 
   afterUpdate(() => {
-    if (shouldAutoScroll && terminalElement) {
+    if (shouldAutoScroll && terminalElement && !isRestoringScroll) {
       terminalElement.scrollTop = terminalElement.scrollHeight;
     }
   });