fix(sessions): clean global store on Hub deletes to prevent ghost session tabs

SessionsHub.handleDelete only updated its local React state via setSessions.
Because the Zustand session store is module-global and survives across
SPA navigation between Hub and TerminalApp, Hub-side deletions left
orphan entries in store.sessions and tabOrder, and never added the id
to deletedIds (which suppresses the 'Session not found' toast). On the
next SPA-nav to /terminal, the orphan id rendered as a ghost tab,
TerminalPane mounted, opened a WebSocket, and the server returned
'Session not found'.

Two-layer fix:
1. SessionsHub.handleDelete: finalize now also calls
   useSessionStore.removeSession(id) (and any companion PTY).
2. TerminalApp.init(): defensive prune of orphans (sessions in store
   but not on the server) before the addSession + render pass.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dorlugasigal

src/frontend/src/components/SessionsHub/SessionsHub.tsx

@@ -173,7 +173,22 @@ export default function SessionsHub() {
         element: element ?? null,
         color: session?.color ?? '#6ec1e4',
         apiDelete: () => deleteSession(id),
-        finalize: () => setSessions((prev) => prev.filter((s) => s.id !== id)),
+        finalize: () => {
+          // Hub deletes must clear the GLOBAL session store too, not just our
+          // local list. The global store may already hold this session if the
+          // user previously visited TerminalApp during the same SPA session
+          // (the Map persists across mount/unmount of TerminalApp). Without
+          // this, a later SPA navigation back to /terminal would re-mount
+          // TerminalPanes for the orphan ids in tabOrder, fail WS attach with
+          // "Session not found", and leak the deleted id back into localStorage.
+          // removeSession also adds the id to deletedIds so any in-flight
+          // attach error toasts are suppressed.
+          const store = useSessionStore.getState();
+          const ms = store.sessions.get(id);
+          if (ms?.companionTermId) store.removeSession(ms.companionTermId);
+          store.removeSession(id);
+          setSessions((prev) => prev.filter((s) => s.id !== id));
+        },
       });
       toast.success(`Session "${session?.name ?? id}" deleted`);
     } catch (err) {

src/frontend/src/components/TerminalApp/TerminalApp.tsx

@@ -169,6 +169,21 @@ export function TerminalApp() {
         const list: Session[] = await fetchSessions();
         const store = useSessionStore.getState();
         const urlSessionId = getSessionIdFromUrl();
+        const serverIds = new Set(list.map((s) => s.id));
+
+        // Defensive prune: the global session store survives across
+        // unmount/remount of TerminalApp (Zustand state is module-global).
+        // If a session was deleted while we were elsewhere (Hub view, code
+        // viewer, etc.), the store may still hold its entry. Clean those up
+        // BEFORE rendering — otherwise TerminalPane mounts for the orphan,
+        // opens a WebSocket, and the server replies "Session not found".
+        // Skip ids currently mid-disintegrate (animation in flight).
+        for (const [id, ms] of store.sessions) {
+          if (!serverIds.has(id) && !ms.exited && !store.dissolvingIds.has(id)) {
+            if (ms.companionTermId) store.removeSession(ms.companionTermId);
+            store.removeSession(id);
+          }
+        }
 
         // Add ALL sessions from server (matching old UI behavior)
         for (const s of list) {