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)

tests/test_sigterm.py

@@ -0,0 +1,69 @@
+"""SIGTERM should stop the server subprocess promptly (<< 30s platform window)."""
+
+from __future__ import annotations
+
+import json
+import os
+import signal
+import subprocess
+import sys
+import time
+import unittest
+import urllib.request
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+class TestSigterm(unittest.TestCase):
+    def test_sigterm_exits_quickly(self) -> None:
+        port = "19090"
+        env = os.environ.copy()
+        env["STRATEGY_ID"] = "sigterm-test"
+        env["PORT"] = port
+        env["HOST"] = "127.0.0.1"
+
+        proc = subprocess.Popen(
+            [sys.executable, "-m", "src.server"],
+            cwd=str(ROOT),
+            env=env,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.PIPE,
+        )
+        try:
+            # wait until health is up
+            url = f"http://127.0.0.1:{port}/health"
+            deadline = time.time() + 5
+            while time.time() < deadline:
+                try:
+                    with urllib.request.urlopen(url, timeout=0.5) as resp:
+                        data = json.loads(resp.read().decode("utf-8"))
+                        if resp.status == 200 and data.get("status") == "ok":
+                            break
+                except Exception:
+                    time.sleep(0.1)
+            else:
+                if proc.poll() is not None:
+                    self.fail(f"server exited before health check: {proc.stderr.read().decode(errors='replace')}")
+                self.fail("server did not become healthy in time")
+
+            t0 = time.time()
+            proc.send_signal(signal.SIGTERM)
+            try:
+                proc.wait(timeout=5)
+            except subprocess.TimeoutExpired:
+                proc.kill()
+                self.fail("server did not exit within 5s after SIGTERM (platform allows ≤30s)")
+            elapsed = time.time() - t0
+            self.assertLess(elapsed, 5.0, f"exit took {elapsed:.2f}s")
+            self.assertEqual(proc.returncode, 0, "SIGTERM must exit cleanly, not kill the process")
+        finally:
+            if proc.poll() is None:
+                proc.kill()
+                proc.wait(timeout=2)
+            if proc.stderr:
+                proc.stderr.close()
+
+
+if __name__ == "__main__":
+    unittest.main()