feat(object-browser): preserve object list on return via stale cache

apps/desktop/src/lib/__tests__/table/contentAreaObjectBrowserCatalog.spec.ts

@@ -36,7 +36,7 @@ describe("ContentArea object browser refresh wiring", () => {
   });
 
   it("exposes object and active table-info reloads as refresh", () => {
-    expect(objectBrowserSource).toMatch(/function refresh\(\): boolean \{\s+void reload\(\);\s+void refreshActiveTableInfo\(\);\s+return true;\s+\}/);
+    expect(objectBrowserSource).toMatch(/function refresh\(\): boolean \{\s+void reload\(\{ preserveExistingRows: true \}\);\s+void refreshActiveTableInfo\(\);\s+return true;\s+\}/);
     expect(objectBrowserSource).toContain("defineExpose({ focusSearch, refresh });");
   });
 

apps/desktop/src/lib/metadata/__tests__/objectBrowserRowsCache.spec.ts

@@ -1,6 +1,6 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import type { ObjectBrowserRow } from "@/lib/table/objectBrowserRows";
-import { cacheObjectBrowserRows, clearObjectBrowserRowsCache, createObjectBrowserRowsCacheWriteToken, getCachedObjectBrowserRows, invalidateObjectBrowserRowsCache } from "@/lib/table/objectBrowserRowsCache";
+import { cacheObjectBrowserRows, clearObjectBrowserRowsCache, createObjectBrowserRowsCacheWriteToken, getCachedObjectBrowserRows, getCachedObjectBrowserRowsForScaffold, invalidateObjectBrowserRowsCache } from "@/lib/table/objectBrowserRowsCache";
 
 const row: ObjectBrowserRow = {
   id: "table:users",
@@ -127,4 +127,43 @@ describe("objectBrowserRowsCache", () => {
     expect(invalidateObjectBrowserRowsCache({ ...scope, tableName: "users" })).toBe(1);
     expect(getCachedObjectBrowserRows(scope)).toBeUndefined();
   });
+
+  describe("scaffold reads (allowStale)", () => {
+    it("returns a fresh hit marked stale=false before the TTL", () => {
+      vi.useFakeTimers();
+      vi.setSystemTime(new Date("2026-07-28T00:00:00Z"));
+      const scope = { connectionId: "c1", database: "db", schema: "public" };
+      cacheRows(scope);
+
+      const hit = getCachedObjectBrowserRowsForScaffold(scope);
+      expect(hit).toBeDefined();
+      expect(hit!.rows).toEqual([row]);
+      expect(hit!.stale).toBe(false);
+      expect(hit!.ageMs).toBe(0);
+      expect(hit!.cachedAt).toBe(Date.now());
+    });
+
+    it("surfaces an expired entry as a stale scaffold instead of refusing it", () => {
+      vi.useFakeTimers();
+      vi.setSystemTime(new Date("2026-07-28T00:00:00Z"));
+      const scope = { connectionId: "c1", database: "db", schema: "public" };
+      cacheRows(scope);
+
+      vi.advanceTimersByTime(30_001);
+      const hit = getCachedObjectBrowserRowsForScaffold(scope);
+      expect(hit).toBeDefined();
+      expect(hit!.rows).toEqual([row]);
+      expect(hit!.stale).toBe(true);
+      expect(hit!.ageMs).toBeGreaterThan(30_000);
+    });
+
+    it("returns undefined when no scaffold is available (uncached or invalidated)", () => {
+      const scope = { connectionId: "c1", database: "db", schema: "public" };
+      expect(getCachedObjectBrowserRowsForScaffold(scope)).toBeUndefined();
+
+      cacheRows(scope);
+      invalidateObjectBrowserRowsCache({ connectionId: "c1", database: "db", schema: "public" });
+      expect(getCachedObjectBrowserRowsForScaffold(scope)).toBeUndefined();
+    });
+  });
 });

apps/desktop/src/lib/table/objectBrowserRowsCache.ts

@@ -78,6 +78,28 @@ export function getCachedObjectBrowserRows(scope: ObjectBrowserRowsCacheScope):
   return hit ? cloneRows(hit.value) : undefined;
 }
 
+export interface ObjectBrowserRowsCacheHit {
+  rows: ObjectBrowserRow[];
+  stale: boolean;
+  ageMs: number;
+  cachedAt: number;
+}
+
+/**
+ * Reads the cached rows for a scope as a **scaffold**, allowing stale entries
+ * (beyond the TTL) to be surfaced and refreshed in the background. This never
+ * adds a new cache entry or expands capacity — a stale hit is the same Map entry
+ * the TTL would otherwise refuse to return, only now with its freshness metadata.
+ *
+ * Carries `stale`/`ageMs`/`cachedAt` so the caller can decide: keep an entry
+ * under TTL as-is, or present it immediately then revalidate in the background.
+ */
+export function getCachedObjectBrowserRowsForScaffold(scope: ObjectBrowserRowsCacheScope): ObjectBrowserRowsCacheHit | undefined {
+  const hit = objectBrowserRowsCache.get(objectBrowserRowsScope(scope), { allowStale: true });
+  if (!hit) return undefined;
+  return { rows: cloneRows(hit.value), stale: hit.stale, ageMs: hit.ageMs, cachedAt: hit.cachedAt };
+}
+
 export function createObjectBrowserRowsCacheWriteToken(scope: ObjectBrowserRowsCacheScope): ObjectBrowserRowsCacheWriteToken {
   const frozenScope = Object.freeze({ ...scope });
   return Object.freeze({ generation: objectBrowserRowsCacheGeneration(frozenScope).generation, scope: frozenScope });