fix(tests): repair test regressions from zod v3 downgrade

- Fix zod/v4 imports in background-task schema tests
- Remove ZWSP prefix from agent-key-remapper test (fixed in #3136)
- Use toMatchObject for openai-only catalog tests (fallback_models added by #3144)
- Replace z.toJSONSchema (zod v4) with zodToJsonSchema (zod v3 compat)
- Fix task-list.ts type narrowing for zod v3 inferred types

src/plugin-handlers/agent-key-remapper.test.ts

@@ -54,7 +54,7 @@ describe("remapAgentKeysToDisplayNames", () => {
     expect(result["hephaestus"]).toBeUndefined()
     expect(result["Prometheus (Plan Builder)"]).toBeDefined()
     expect(result["prometheus"]).toBeUndefined()
-    expect(result["\u200BAtlas (Plan Executor)"]).toBeDefined()
+    expect(result["Atlas (Plan Executor)"]).toBeDefined()
     expect(result["atlas"]).toBeUndefined()
     expect(result["Athena (Council)"]).toBeDefined()
     expect(result["athena"]).toBeUndefined()