feat(chats): add managed projectless chat sessions

Create projectless chat sessions under a managed, date-scoped Chats directory and clean abandoned or deleted session folders.

Add Chats to sidebar state, startup cache, shared context, and Electron Mini Chat while keeping VS Code project-only. Resolve managed chat directories to one server-side memory owner and document the runtime contracts.

packages/ui/src/stores/globalSessions.ts

@@ -3,6 +3,7 @@ import { runBackgroundNetworkTask } from '@/lib/background-network';
 import { retry } from "@/sync/retry";
 import { stripSessionListDetails } from "@/sync/sanitize";
 import { startSessionLoadPerformanceEvent } from "@/sync/session-load-performance";
+import { isChatDirectoryPath } from '@/lib/chatDirectories';
 
 export type GlobalSessionRecord = Session & {
     project?: {
@@ -12,6 +13,12 @@ export type GlobalSessionRecord = Session & {
     } | null;
 };
 
+export const filterManagedChatsForRuntime = (sessions: Session[], vscode: boolean): Session[] => (
+    vscode
+        ? sessions.filter((session) => !isChatDirectoryPath(session.directory))
+        : sessions
+);
+
 const toNumber = (value: string | null): number | null => {
     if (!value) {
         return null;