feat: refresh OpenVINO GenAI NPU worker prototype

openvino-genai-npu-worker/CONTRACT.md

@@ -1,6 +1,6 @@
 # Bounded OpenVINO GenAI NPU worker contract
 
-Status: proposed prototype contract; not a live Atlas/Hermes routing dependency.
+Status: prototype contract implemented locally; not a live Atlas/Hermes routing dependency.
 Default address: `http://127.0.0.1:18820`.
 
 ## Purpose and hard boundary
@@ -167,7 +167,7 @@ Validation/error behavior:
 
 - Unsupported path: `404` JSON `{"error":"not found"}`.
 - Unsupported job, empty input, too-long input, invalid token bound, missing model, or generation failure: JSON `{"error":"..."}` with non-2xx preferred for future implementations. The current stdlib prototype returns `400` for these errors.
-- If `npu_busy_delta_us <= 0`, the response should be treated as failed by smoke tests even if an HTTP handler emitted `200`.
+- If `npu_busy_delta_us <= 0`, the response should be treated as failed by smoke tests even if an HTTP handler emitted `200`; the refreshed prototype returns `503` with the generation payload plus an `error` field.
 
 ## Prompt/job contract
 
@@ -253,6 +253,13 @@ Also verify the temporary listener is gone:
 ss -ltnp | grep ':18820' && { echo 'temporary smoke server still running'; exit 1; } || true
 ```
 
+Unit tests that do not load the model or require private data:
+
+```bash
+cd /home/will/lab/swarm/openvino-genai-npu-worker
+python -m pytest -q
+```
+
 ## NPU busy-time verification plan
 
 Acceptance for any NPU claim requires all of the following: