feat(cloud): show purchased plan revision alongside the latest revision

- Expose the workspace's purchased plan revision from the entitlement
  snapshot.
- Stack the purchased revision card in front of the latest revision in
  the plan comparison dialog; both cards share the same layout, and the
  purchased card's copy and prices come from the Space revision endpoint
  while benefits stay on the entitlement snapshot.
- Add a cancel-first tooltip for subscribing to the newer revision.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

web/src/app/infra/entities/workspace.ts

@@ -24,6 +24,14 @@ export interface WorkspaceMembership {
 }
 
 export interface CurrentWorkspace {
+  current_plan?: {
+    subscription_started_at?: number | null;
+    name: string;
+    revision: number;
+    limits: Record<string, number>;
+    entitlement_features: Record<string, boolean>;
+    monthly_bonus_credits: number;
+  } | null;
   workspace: Workspace;
   membership: WorkspaceMembership;
   permissions: string[];