fix: prevent cascade rollback from restoring deleted session descendants (#1555)

The OpenCode server cascade-deletes all child sessions when a parent
is removed. The client was sending individual DELETE requests for each
descendant, which returned 404 after the parent's cascade removed them.
The 404 triggered rollback in deleteSessionAction, restoring already-
deleted sessions back into the global store.

Changes:
- executeDeleteSession: only send the root session delete; the server
  cascade handles descendants.
- deleteSession / deleteSessionInDirectory: treat 404 in catch as
  success, acting as a safety net for remaining paths (e.g. sidebar
  bulk action bar when parent and child are both selected).

packages/ui/src/sync/session-actions.ts

@@ -483,6 +483,12 @@ export async function deleteSession(sessionId: string, _options?: Record<string,
     return true
   } catch (error) {
     console.error("[session-actions] deleteSession failed", error)
+    // The server cascade-deletes child sessions when the parent is removed.
+    // Subsequent delete attempts for those children return 404; treat as
+    // success since the session was already deleted by the cascade.
+    if ((error as { status?: number })?.status === 404) {
+      return true
+    }
     restoreSessionListSnapshots(snapshots)
     restoreGlobalSessionSnapshot(globalSnapshot)
     return false
@@ -507,6 +513,9 @@ export async function deleteSessionInDirectory(sessionId: string, directory: str
     return true
   } catch (error) {
     console.error("[session-actions] deleteSessionInDirectory failed", error)
+    if ((error as { status?: number })?.status === 404) {
+      return true
+    }
     restoreSessionListSnapshots(snapshots)
     restoreGlobalSessionSnapshot(globalSnapshot)
     return false