[Ubuntu 22.04][Agent&Skills] dcode -n managed non-interactive mode exits 0 but outputs error instead of LLM response

## Description

When running `dcode` in managed non-interactive mode (`dcode -n "..."`), the command exits with code 0 (success) but the output contains a managed non-interactive error message instead of the expected LLM response. The LangGraph server starts successfully and reports Ready, but the agent inference call fails with `error_class=unknown` and the result is an error string rather than the task output. Any caller that checks the output content (rather than the exit code) will fail to find the expected response.

Platform scope: Reproduced on Ubuntu 22.04 and Ubuntu 24.04 GPU. Passes on Ubuntu 24.04 (non-GPU), Ubuntu 26.04 GPU, macOS, WSL ARM. Failure is inconsistent across platforms; may be related to inference provider or sandbox resource availability.

Regression: Unknown — earlier versions not tested.

## Environment

```text
Device: CI runner (Ubuntu 22.04, Ubuntu 24.04 GPU)
OS: Ubuntu 22.04 / Ubuntu 24.04 GPU
Architecture: x86_64
Node.js: v22.23.1
npm: Not captured
Docker: Not captured
OpenShell CLI: openshell 0.0.85
NemoClaw: v0.0.100
OpenClaw: N/A (Deep Agents Code agent, dcode v0.1.34)
```

## Steps to Reproduce

1. Onboard a Deep Agents Code sandbox with nvidia-prod inference provider
2. Run:
```bash
nemoclaw {sandbox-name} exec -- dcode -n "PING"
```
3. Observe the command exits 0 but the output does not contain the expected response

## Expected Result

`dcode -n "PING"` exits 0 and the output contains `PING` (or similar acknowledgment from the LLM).

## Actual Result

`dcode -n` exits 0 but the output is:

```text
Running task non-interactively...
App: v0.1.34 | Agent: agent (default) | Model: nvidia/nemotron-3-ultra-550b-a55b
| Thread: {thread-id}
Starting LangGraph server...
v Server ready
managed non-interactive error: error_class=unknown category=unknown retryable=false correlation_id={id}

Unexpected error (correlation_id={id})
EXITCODE:0
```

The output does not contain `PING`. The process exits 0 despite the error, so callers relying on exit code cannot detect the failure.

## Logs

Not captured