Set scopa targets to their traditional defaults

Partnership games go to 21: scopone scientifico (the tournament target)
and scopa a quattro, while two-player scopa keeps its usual 11. The scopa
package resolves the default from the player count and exposes a per
variant options_schema default, so the lobby creation form shows the
right value without frontend changes.

server/packages/tavolo-scopone/README.md

@@ -19,7 +19,8 @@ implementation.
 - `plugin.py` — `ScoponeEngine(GameEngine)`: the platform-facing adapter.
   It translates create/join/websocket actions/deadlines into rules-engine
   calls and back, validates the `target_score`/`napola`/`asso_pigliatutto`
-  creation options, and extracts the `MatchResult` (teams, winner,
+  creation options (the match target defaults to the traditional 21
+  points), and extracts the `MatchResult` (teams, winner,
   per-player scores and the match summary persisted as the match's JSON
   `result`).
 

server/packages/tavolo-scopone/src/tavolo/scopone/state.py

@@ -37,7 +37,9 @@ PHASE_PLAYING = "playing"
 PHASE_HAND_END = "hand_end"
 PHASE_FINISHED = "finished"
 
-DEFAULT_TARGET_SCORE = 11
+# The traditional match target for scopone scientifico: the partnership
+# game is played to 21 points.
+DEFAULT_TARGET_SCORE = 21
 
 
 def team_of(seat: int) -> int:

server/packages/tavolo-scopone/tests/test_plugin.py

@@ -35,7 +35,8 @@ class CreateTest(unittest.TestCase):
         session = _session(engine)
         self.assertEqual("A", session.players[0].team)
         self.assertIsInstance(session.state, ScoponeState)
-        self.assertEqual(11, session.state.target_score)
+        # The traditional partnership target.
+        self.assertEqual(21, session.state.target_score)
         self.assertTrue(session.state.napola)
 
     def test_create_options(self) -> None: