fix(gsd): cast unknown gate id in test to satisfy GateId type

The gate-registry test intentionally passes an invalid gate id "Q999"
to verify error handling, but the strict GateId union type rejects it
at compile time. Cast to GateId to fix the typecheck:extensions CI step.

src/resources/extensions/gsd/tests/gate-registry.test.ts

@@ -101,7 +101,7 @@ describe("assertGateCoverage", () => {
 
   test("throws when a row has an unknown gate id", () => {
     assert.throws(
-      () => assertGateCoverage([{ gate_id: "Q999" }], "gate-evaluate", { requireAll: false }),
+      () => assertGateCoverage([{ gate_id: "Q999" as GateId }], "gate-evaluate", { requireAll: false }),
       (err: Error) => err.message.includes("Q999"),
     );
   });