fix(cli,hub): resolve typecheck errors in codex reasoning effort (#432)

* fix(cli,hub): resolve typecheck errors in codex reasoning effort and notification test

- Cast `getModelReasoningEffort()` return (string | null) to
  `ReasoningEffort | undefined` at three call sites in
  codexLocalLauncher.ts and runCodex.ts where the narrower type is
  expected.
- Add missing `modelReasoningEffort: null` default in
  notificationHub.test.ts to satisfy the Session type contract.

These errors were introduced in 79a13d2 and have been failing CI on
main since 2026-04-10.

* fix(cli): add missing getModelReasoningEffort to test mock session

The test stub in codexLocalLauncher.test.ts was missing the
getModelReasoningEffort method added in 79a13d2, causing runtime
TypeError in CI.

cli/src/codex/codexLocalLauncher.test.ts

@@ -79,6 +79,7 @@ function createSessionStub(permissionMode: 'default' | 'read-only' | 'safe-yolo'
                 }
             },
             getPermissionMode: () => permissionMode,
+            getModelReasoningEffort: () => null,
             onSessionFound: () => {},
             sendSessionEvent: (event: { type: string; message?: string }) => {
                 sessionEvents.push(event);