fix(combo): restore missing preferAntigravityConnectionsWithStoredProject

quotaStrategies imported the reset-aware pool filter from
../antigravityProjectPersistence.ts, a module that does not exist — the
helper belongs in antigravityProjectPersist.ts and was never added there,
breaking typecheck. Add the helper alongside the persist path, point the
import at the real module, and cover the filter with unit tests.

tests/unit/antigravity-project-persist-pool-filter.test.ts

@@ -0,0 +1,32 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { preferAntigravityConnectionsWithStoredProject } from "@omniroute/open-sse/services/antigravityProjectPersist.ts";
+
+test("keeps connections with a projectId on the column or in providerSpecificData", () => {
+  const kept = preferAntigravityConnectionsWithStoredProject([
+    { id: "a", projectId: "projects/a" },
+    { id: "b", providerSpecificData: { projectId: "projects/b" } },
+  ]);
+
+  assert.deepEqual(
+    kept.map((c) => c.id),
+    ["a", "b"]
+  );
+});
+
+test("drops connections whose projectId is missing, blank or not a string", () => {
+  const kept = preferAntigravityConnectionsWithStoredProject([
+    { id: "missing" },
+    { id: "blank", projectId: "   " },
+    { id: "null", projectId: null },
+    { id: "numeric", projectId: 42 },
+    { id: "blank-psd", providerSpecificData: { projectId: "" } },
+    { id: "null-psd", providerSpecificData: null },
+  ]);
+
+  assert.deepEqual(kept, []);
+});
+
+test("returns an empty pool for an empty input instead of throwing", () => {
+  assert.deepEqual(preferAntigravityConnectionsWithStoredProject([]), []);
+});