feat: add hand detail API and enrich hand summary fields

- HandSummary: add hole_cards, starting_stacks, ending_stacks, pot_contributions
- Engine: capture all players' hole cards (not just showdown), pre/post hand stacks, per-level pot contributions
- Server: new GET /game/<game_id>/hands/<hand_number> route
- Service: add get_hand_state() method
- Tests: add ServerTests for new endpoint, update existing tests
- Existing GET /game/<game_id> auto-inherits new fields via shared to_dict()

tests/test_server.py

@@ -0,0 +1,76 @@
+import json
+import unittest
+from threading import Thread
+from urllib.request import Request, urlopen
+
+from texas_holdem import server as poker_server
+from texas_holdem.service import GameManager
+
+
+class ServerTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self.previous_manager = poker_server.MANAGER
+        poker_server.MANAGER = GameManager()
+        self.server = poker_server.create_server("127.0.0.1", 0)
+        self.thread = Thread(target=self.server.serve_forever, daemon=True)
+        self.thread.start()
+        host, port = self.server.server_address
+        self.base_url = f"http://{host}:{port}"
+
+    def tearDown(self) -> None:
+        self.server.shutdown()
+        self.server.server_close()
+        self.thread.join(timeout=2)
+        poker_server.MANAGER = self.previous_manager
+
+    def request_json(
+        self,
+        method: str,
+        path: str,
+        payload: dict[str, object] | None = None,
+    ) -> dict[str, object]:
+        data = None
+        headers = {}
+        if payload is not None:
+            data = json.dumps(payload).encode("utf-8")
+            headers["Content-Type"] = "application/json"
+        request = Request(
+            f"{self.base_url}{path}",
+            data=data,
+            headers=headers,
+            method=method,
+        )
+        with urlopen(request, timeout=5) as response:
+            return json.loads(response.read().decode("utf-8"))
+
+    def test_get_hand_route_returns_expanded_hand_summary(self) -> None:
+        self.request_json(
+            "POST",
+            "/game",
+            {
+                "game_id": "route-demo",
+                "seed": 17,
+                "starting_stack": 200,
+                "small_blind": 5,
+                "big_blind": 10,
+                "players": [
+                    {"id": "a", "type": "calling"},
+                    {"id": "b", "type": "calling"},
+                ],
+            },
+        )
+        self.request_json("POST", "/game/route-demo/hands", {"count": 1})
+
+        hand = self.request_json("GET", "/game/route-demo/hands/1")
+        game = self.request_json("GET", "/game/route-demo")
+
+        self.assertEqual(hand["hand_number"], 1)
+        self.assertEqual(set(hand["hole_cards"]), {"a", "b"})
+        self.assertEqual(hand["starting_stacks"], {"a": 200, "b": 200})
+        self.assertIn("ending_stacks", hand)
+        self.assertIn("pot_contributions", hand)
+        self.assertEqual(game["hands"][0], hand)
+
+
+if __name__ == "__main__":
+    unittest.main()