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_strategy_startup.py

@@ -0,0 +1,57 @@
+"""Missing STRATEGY_ID must cause startup failure (exit non-zero)."""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+import unittest
+from pathlib import Path
+from unittest import mock
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+class TestStrategyStartup(unittest.TestCase):
+    def test_missing_strategy_id_exits_nonzero(self) -> None:
+        env = os.environ.copy()
+        env["STRATEGY_ID"] = ""
+        env["PORT"] = "19081"
+        env["HOST"] = "127.0.0.1"
+        proc = subprocess.run(
+            [sys.executable, "-m", "src.server"],
+            cwd=str(ROOT),
+            env=env,
+            capture_output=True,
+            text=True,
+            timeout=10,
+        )
+        self.assertNotEqual(proc.returncode, 0)
+        self.assertIn("STRATEGY_ID", proc.stderr)
+
+    def test_whitespace_strategy_id_exits_nonzero(self) -> None:
+        env = os.environ.copy()
+        env["STRATEGY_ID"] = "   "
+        env["PORT"] = "19082"
+        env["HOST"] = "127.0.0.1"
+        proc = subprocess.run(
+            [sys.executable, "-m", "src.server"],
+            cwd=str(ROOT),
+            env=env,
+            capture_output=True,
+            text=True,
+            timeout=10,
+        )
+        self.assertNotEqual(proc.returncode, 0)
+
+    def test_require_strategy_id_helper(self) -> None:
+        from src.strategy import require_strategy_id
+
+        with self.assertRaises(SystemExit) as ctx:
+            with mock.patch.dict(os.environ, {"STRATEGY_ID": ""}, clear=False):
+                require_strategy_id()
+        self.assertNotEqual(ctx.exception.code, 0)
+
+
+if __name__ == "__main__":
+    unittest.main()