fix: improve cross-device evidence and exploration lifecycle

Align Responses cache affinity across execution and summary calls, preserve required checks and evidence uncertainty, and allow safe deletion of inactive explorations while retaining independent reruns.

Validation: backend suite passed except intentional prompt golden drift, then all 17 transcript tests passed after snapshot refresh; 268 frontend tests and production build passed; Ruff, quality ratchet and core type checks passed.

apps/showcase_ui/src/app/components/agent-stream/agent-stream.component.ts

@@ -294,6 +294,7 @@ export class AgentStreamComponent implements AfterViewInit {
   public isTaskDropdownOpen = signal<boolean>(false);
   public isNotesDropdownOpen = signal<boolean>(false);
   public isAutomationOpen = signal(false);
+  public deleteError = signal('');
 
   // Run info popover (opened from the Flash / Pro chip): elapsed time, token
   // usage, executor context share and the Pro tuning the run started with.
@@ -997,12 +998,13 @@ export class AgentStreamComponent implements AfterViewInit {
 
   public deleteTask(sessionId: string, event?: Event): void {
     if (event) event.stopPropagation();
-    if (!confirm("确定删除此任务？此操作无法撤销。")) {
+    if (!confirm(this.agentService.deletionPrompt(sessionId))) {
       return;
     }
+    this.deleteError.set('');
     this.agentService.deleteSession(sessionId).subscribe({
       error: (err) => {
-        console.error(`删除会话失败：${sessionId}:`, err);
+        this.deleteError.set(err.error?.detail || "删除失败，请稍后重试");
       }
     });
   }