[docker/cli] Support platform selection in `docker sandbox` command

### ROOT CAUSE The `docker sandbox` command does not support the `--platform` flag, preventing users from specifying the target architecture/platform. This limitation forces users on macOS (which runs containers on Linux/arm64) to use ARM-based containers, even if they need x86_64 compatibility. ### CODE FIX Modify the `docker sandbox` command to accept a `--platform` flag, which is then passed to the underlying `docker run` command. This requires updating the command's flag handling and the container creation logic. 1. **Add the `--platform` flag** to the `sandbox` command: ```go // In the sandbox command definition (e.g., commands/sandbox.go) var cmd sandboxCommand flags := cmd.Flags() flags.StringVar(&cmd.platform, "platform", "", "platform in the format of os/cpu, e.g., linux/amd64") ``` 2. **Pass the platform flag** during container creation: ```go // In the Run method of the sandbox command args := []string{"run", "--rm", "--name", "sandbox", "-it", "docker-cli:latest", "/bin/sh"} if cmd.platform != "" { args = append(args, "--platform", cmd.platform) } // Execute the command using the updated args ``` 3. **Handle platform validation** (optional, for user feedback): ```go // Add validation to ensure the platform string is in a valid format if cmd.platform != "" && !isValidPlatform(cmd.platform) { return fmt.Errorf("invalid platform: %s", cmd.platform) } ``` This change allows users to specify `--platform linux/amd64` or any valid platform string, overriding the default platform detection.