fix: drop game_number by one for finished playoff cards

Scoreboard payloads don't include gameNumber, so the previous fix fell straight through to series_state['game_number'], which is hi+lo+1 — the *next* game. Once a game goes FINAL the win for this game is already banked in seriesStatus, so the card's own number is hi+lo. For the just-played Game 1 of Kings/Avalanche (series now 1-0), this brings the header back to "Game 1 of 7" instead of "Game 2 of 7".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_playoff_series.py

@@ -149,10 +149,17 @@ class TestSeriesSummary:
         game = make_playoff_game(top_wins=1, bottom_wins=1)
         assert series_summary(game) == "Game 3 of 7"
 
-    def test_finished_game_keeps_its_own_number(self):
-        # seriesStatus has advanced to 2-0 after this game finished, but the
-        # raw gameNumber pins the card to the game it actually represents.
-        game = make_playoff_game(top_wins=2, bottom_wins=0, game_number=2)
+    def test_finished_game_uses_pre_advance_number(self):
+        # Scoreboard payloads don't carry gameNumber. Once a game goes FINAL,
+        # seriesStatus already includes this game's result, so the card's game
+        # number is hi+lo, not hi+lo+1.
+        game = make_playoff_game(top_wins=1, bottom_wins=0, game_state="FINAL")
+        assert series_summary(game) == "Game 1 of 7"
+
+    def test_finished_game_honors_explicit_game_number(self):
+        game = make_playoff_game(
+            top_wins=2, bottom_wins=0, game_state="FINAL", game_number=2
+        )
         assert series_summary(game) == "Game 2 of 7"