Server-side scenario execution: thin effects client replaces local engine

- engine/ (DagWalker, sessions, IndexedDbPlanStore) deleted; server owns the graph
- trigger/callback/counter carry PendingEffect; GET /sdk/v1/scenarios/pending polled
  (30s jittered heartbeat paused on hidden tab + wait-deadline timers)
- client.effects public API unchanged (done/buy/dismiss/end/claim/battlepass/quest)
- planStateStore removed; loginEvent kept; reconcile() makes server the source of truth
- generated models regenerated; skills/README/CHANGELOG updated

test/PublicApi.test.ts

@@ -64,7 +64,7 @@ describe('public API surface', () => {
     const client = new RudderClient({
       baseUrl: 'https://api.test.rudder.build',
       projectKey: 'test-project',
-      runtime: { planStateStore: null, loginEvent: null },
+      runtime: { loginEvent: null },
     });
 
     expect(client.effects).toBeDefined();
@@ -75,7 +75,7 @@ describe('public API surface', () => {
     const client = new RudderClient({
       baseUrl: 'https://api.test.rudder.build',
       projectKey: 'test-project',
-      runtime: { planStateStore: null, loginEvent: null },
+      runtime: { loginEvent: null },
     });
 
     expect(client.remoteConfig).toBeDefined();