feat(FN-2160): add push-after-merge remote sync workflow

- Add project settings for pushAfterMerge and pushRemote with defaults and typed merge result fields for push status/errors
- Implement post-merge remote sync in the merger with pull --rebase, auto/AI conflict resolution, and one non-fast-forward retry before push
- Expose push-after-merge controls in Settings modal with conditional Push Remote input and coverage for desktop/mobile save flows
- Document the new settings in the settings reference and stabilize CLI cross-build help test timeout

packages/cli/src/__tests__/build-exe-cross.test.ts

@@ -134,7 +134,7 @@ describe("build-exe-cross: --all builds all platforms", () => {
     }
     expect(result.status).toBe(0);
     expect(result.stdout).toContain("fn");
-  });
+  }, 20_000);
 });
 
 describe("build-exe-cross: default (no args) backward compatibility", () => {