docs+store: oracle r3 follow-ups

- README test/smoke counts: 18→22, 26→28 (drifted across rounds)
- runLiveFetch keepCurrent now checks the MERGED catalog, not the old
  state — fixes the edge case where a scenarioId disappears between
  refreshes (would have orphaned the active scenario)

Constraint: no test changes; pure cleanup
Confidence: high
Scope-risk: narrow

README.md

@@ -95,14 +95,14 @@ pnpm fetch:scenarios
 pnpm dev                                # → http://127.0.0.1:5173
 
 # tests
-pnpm test                               # vitest, 18 tests across api, live,
-                                        # synthetic, layout
+pnpm test                               # vitest, 22 tests across api, live,
+                                        # synthetic, layout, store
 
 # build
 pnpm build                              # tsc + vite, single chunk ~225 KB gz
 
 # end-to-end smoke + screenshots
-pnpm qa:smoke                           # playwright headless, 26 assertions
+pnpm qa:smoke                           # playwright headless, 28 assertions
 
 # DOM layout audit
 pnpm qa:layout

src/state/store.ts

@@ -83,14 +83,15 @@ async function runLiveFetch(
     const { scenarios, workItems, distinctDefs } = await buildLiveScenariosFromApi();
     const merged = [...scenarios, ...syntheticScenarios];
     const first = merged[0];
-    const keepCurrent = get().scenarios.some((s) => s.id === get().scenarioId);
+    const currentId = get().scenarioId;
+    const stillThere = merged.find((s) => s.id === currentId);
     set({
       scenarios: merged,
       liveTotals: { workItems: workItems.length, distinctDefs },
       liveFetchedAt: Date.now(),
       liveLoading: false,
-      scenarioId: keepCurrent ? get().scenarioId : first?.id ?? get().scenarioId,
-      selectedStepId: keepCurrent ? get().selectedStepId : first?.defaultStepId ?? null,
+      scenarioId: stillThere ? currentId : first?.id ?? currentId,
+      selectedStepId: stillThere ? get().selectedStepId : first?.defaultStepId ?? null,
     });
     get().pushToast(
       "ok",