Phase1 skeleton: replace demo main.py with src.server contract

- Overlay ModelHub XC Phase1 (health/status, STRATEGY_ID gate, dry-run)
- Dockerfile CMD -> python -m src.server; FROM stays platform TCR base
- Remove demo main.py and requirements.txt (stdlib only)
- Add tests/, scripts/, docs/, Makefile, config/examples (no secrets)

config/candidates.example.json

@@ -0,0 +1,21 @@
+{
+  "candidates": [
+    {
+      "model_id": "example-org/example-model",
+      "modelAddress": "example-org/example-model",
+      "taskType": "text-generation",
+      "targetGpu": "Iluvatar_bi-100",
+      "framework": "vllm",
+      "notes": "Phase1 example only — not a real submit payload"
+    },
+    {
+      "model_id": "example-org/another-model",
+      "taskType": "text-generation",
+      "notes": "Minimal fields: model_id required; others optional"
+    }
+  ],
+  "_meta": {
+    "description": "Minimal dry-run input schema for Phase1",
+    "pending_align": "Future Phase2 may read /workspace/modelhub-adapt/pending-submit.md A→B order"
+  }
+}