feat(ui): add back button to session view and auto-clear active session on instance stop

packages/ui/src/App.tsx

@@ -217,6 +217,7 @@ const App: Component = () => {
 
     if (!confirmed) return
 
+    clearActiveParentSession(instanceId)
     await stopInstance(instanceId)
   }
 

packages/ui/src/components/instance/instance-shell2.tsx

@@ -66,7 +66,7 @@ import SessionView from "../session/session-view"
 import { Sidebar, type FileNode } from "./sidebar"
 import { Editor } from "./editor"
 import { serverApi } from "../../lib/api-client"
-import { Sparkles, Layout as LayoutIcon, Terminal as TerminalIcon, Search, Loader2, Zap, Shield, Settings, FileArchive } from "lucide-solid"
+import { Sparkles, Layout as LayoutIcon, Terminal as TerminalIcon, Search, Loader2, Zap, Shield, Settings, FileArchive, ArrowLeft } from "lucide-solid"
 import { formatTokenTotal } from "../../lib/formatters"
 import { sseManager } from "../../lib/sse-manager"
 import { getLogger } from "../../lib/logger"
@@ -1342,6 +1342,14 @@ Now analyze the project and report your findings.`
           <div class="flex items-center space-x-4">
             <Show when={activeSessionIdForInstance() && activeSessionIdForInstance() !== "info"}>
               <div class="flex items-center space-x-2">
+                <button
+                  onClick={() => props.onCloseSession(activeSessionIdForInstance()!)}
+                  class="flex items-center gap-1.5 px-2.5 py-1 text-[11px] font-semibold text-zinc-400 hover:text-white hover:bg-white/10 border border-transparent hover:border-white/10 transition-all rounded-full"
+                  title="Back to Sessions"
+                >
+                  <ArrowLeft size={14} strokeWidth={2} />
+                  <span>Back</span>
+                </button>
                 {/* Compact Button */}
                 <button
                   onClick={handleCompact}