Add briscola: classic two-player and briscola a quattro

New tavolo-briscola distribution implementing briscola on the platform:

- pure rules (state.py, engine.py): 3-card deals, a face-up trump that
  is the last card drawn, trump-first trick resolution (A > 3 > K > H >
  J > 7 > 6 > 5 > 4 > 2), 120 points per deal, 60-60 patta re-deals, a
  configurable target score (default 61), deal-end acknowledgements and
  turn auto-play;
- BriscolaEngine (briscola, 2 players) and BriscolaQuattroEngine
  (briscola_a_quattro, 4 players in fixed partnerships) adapters;
- registered in tavolo-app, packaged in the Docker image, documented.

Platform fixes surfaced by a two-player lobby:

- the websocket state and snapshot payloads now carry seats_open (they
  were only in the REST lobby payload), so lobbies with player counts
  other than four render correctly; seats_open is clamped at zero;
- the web client logs unparseable server messages instead of silently
  dropping them.

Web client: briscola table for both variants (stock, face-up trump,
trick, last-trick banner), deal summary modal and game-over overlay.

Tests: tavolo-briscola rules/adapter suites, app integration tests
(lobby, websocket play, turn timeout, deal-end acks, persistence), a
platform seats_open test and frontend model parsing tests.

web/src/model.rs

@@ -26,6 +26,9 @@ pub struct PlayerView {
     pub captured_count: usize,
     #[serde(default)]
     pub scope: i32,
+    /// Briscola: point value of the player's captured pile.
+    #[serde(default)]
+    pub points: i32,
     /// Own hand only; absent for the other players.
     #[serde(default)]
     pub hand: Option<Vec<String>>,
@@ -54,6 +57,38 @@ pub struct MoveView {
     pub pigliatutto: bool,
 }
 
+/// One card played in the current briscola trick, in play order.
+#[derive(Debug, Clone, Deserialize)]
+#[allow(dead_code)]
+pub struct TrickCard {
+    pub seat: usize,
+    pub card: String,
+}
+
+/// The most recently completed briscola trick.
+#[derive(Debug, Clone, Deserialize)]
+#[allow(dead_code)]
+pub struct LastTrick {
+    pub winner: usize,
+    #[serde(default)]
+    pub cards: Vec<TrickCard>,
+}
+
+/// The scoring breakdown of one completed briscola deal.
+#[derive(Debug, Clone, Deserialize)]
+#[allow(dead_code)]
+pub struct DealSummary {
+    #[serde(default)]
+    pub deal: i32,
+    /// A 60-60 deal: its points are discarded and the deal is replayed.
+    #[serde(default)]
+    pub patta: bool,
+    pub points: Scores,
+    pub totals: Scores,
+    #[serde(default)]
+    pub cards: Option<TeamCounts>,
+}
+
 #[derive(Debug, Clone, Copy, Deserialize)]
 pub struct TeamCounts {
     #[serde(rename = "A")]
@@ -168,6 +203,30 @@ pub struct GameView {
     /// Legal captures per hand card; present only for the player on turn.
     #[serde(default)]
     pub legal_moves: Option<HashMap<String, Vec<Vec<String>>>>,
+    /// Briscola: number of seats at the table (2 or 4).
+    #[serde(default)]
+    pub player_count: usize,
+    /// Briscola: trump suit of the current deal (empty for other games).
+    #[serde(default)]
+    pub briscola_suit: String,
+    /// Briscola: the face-up trump card, until it is drawn.
+    #[serde(default)]
+    pub briscola_card: Option<String>,
+    /// Briscola: face-down cards left in the stock.
+    #[serde(default)]
+    pub stock_count: usize,
+    /// Briscola: cards of the trick in progress, in play order.
+    #[serde(default)]
+    pub trick: Vec<TrickCard>,
+    /// Briscola: seat that led the current trick.
+    #[serde(default)]
+    pub trick_leader: Option<usize>,
+    /// Briscola: the most recently completed trick.
+    #[serde(default)]
+    pub last_trick: Option<LastTrick>,
+    /// Briscola: scoring breakdown of the most recent deal.
+    #[serde(default)]
+    pub last_deal: Option<DealSummary>,
 }
 
 #[derive(Debug, Deserialize)]
@@ -567,6 +626,22 @@ pub fn card_asset(code: &str) -> String {
     format!("/assets/cards/{code}.svg")
 }
 
+/// Whether a game type is one of the briscola variants.
+pub fn is_briscola(game_type: &str) -> bool {
+    game_type == "briscola" || game_type == "briscola_a_quattro"
+}
+
+/// Human-readable suit name for a one-letter code (`D` -> "denari").
+pub fn suit_name(suit: &str) -> String {
+    match suit {
+        "D" => "denari".to_string(),
+        "C" => "coppe".to_string(),
+        "S" => "spade".to_string(),
+        "B" => "bastoni".to_string(),
+        _ => suit.to_string(),
+    }
+}
+
 pub const CARD_BACK: &str = "/assets/cards/back.svg";
 
 /// Display order key for a hand: rank ascending (01..10, i.e. 1..7 then
@@ -1054,4 +1129,112 @@ mod tests {
         assert!(g.default_options().is_empty());
         assert_eq!(0, g.min_players);
     }
+
+    #[test]
+    fn is_briscola_matches_both_variants() {
+        assert!(is_briscola("briscola"));
+        assert!(is_briscola("briscola_a_quattro"));
+        assert!(!is_briscola("scopone_scientifico"));
+        assert_eq!("denari", suit_name("D"));
+        assert_eq!("coppe", suit_name("C"));
+        assert_eq!("spade", suit_name("S"));
+        assert_eq!("bastoni", suit_name("B"));
+        assert_eq!("?", suit_name("?"));
+    }
+
+    #[test]
+    fn game_view_parses_briscola_payload() {
+        let g: GameView = serde_json::from_value(json!({
+            "id": "b1",
+            "join_code": "ABC123",
+            "game_type": "briscola",
+            "phase": "playing",
+            "target_score": 61,
+            "player_count": 2,
+            "hand_number": 1,
+            "dealer": 0,
+            "turn": 1,
+            "scores": {"A": 0, "B": 0},
+            "briscola_suit": "D",
+            "briscola_card": "07D",
+            "stock_count": 33,
+            "trick": [{"seat": 1, "card": "04C"}],
+            "trick_leader": 1,
+            "last_trick": null,
+            "players": [
+                {"sub": "alice", "name": "Alice", "seat": 0, "team": "A",
+                 "cards_left": 3, "captured_count": 0, "points": 0,
+                 "hand": ["01D"]},
+                {"sub": "bob", "name": "Bob", "seat": 1, "team": "B",
+                 "cards_left": 3, "captured_count": 0, "points": 0},
+            ],
+            "last_deal": null,
+            "acknowledged": [],
+            "hand_end_deadline": null,
+            "turn_deadline": "2026-01-01T00:00:30+00:00",
+            "your_turn": true,
+        }))
+        .unwrap();
+        assert!(is_briscola(&g.game_type));
+        assert_eq!("D", g.briscola_suit);
+        assert_eq!(Some("07D".to_string()), g.briscola_card);
+        assert_eq!(33, g.stock_count);
+        assert_eq!(1, g.trick.len());
+        assert_eq!(1, g.trick[0].seat);
+        assert_eq!("04C", g.trick[0].card);
+        assert_eq!(Some(1), g.trick_leader);
+        assert_eq!(0, g.players[0].points);
+        assert_eq!(Some(true), g.your_turn);
+    }
+
+    #[test]
+    fn game_view_parses_briscola_deal_summary() {
+        let g: GameView = serde_json::from_value(json!({
+            "id": "b1",
+            "game_type": "briscola_a_quattro",
+            "phase": "hand_end",
+            "player_count": 4,
+            "scores": {"A": 55, "B": 65},
+            "last_deal": {
+                "deal": 1,
+                "patta": false,
+                "points": {"A": 55, "B": 65},
+                "totals": {"A": 55, "B": 65},
+                "cards": {"A": 19, "B": 21},
+            },
+            "last_trick": {
+                "winner": 3,
+                "cards": [
+                    {"seat": 0, "card": "02D"},
+                    {"seat": 1, "card": "05D"},
+                    {"seat": 2, "card": "04D"},
+                    {"seat": 3, "card": "07D"},
+                ],
+            },
+        }))
+        .unwrap();
+        let deal = g.last_deal.unwrap();
+        assert_eq!(1, deal.deal);
+        assert!(!deal.patta);
+        assert_eq!(Scores { a: 55, b: 65 }, deal.points);
+        assert_eq!(Scores { a: 55, b: 65 }, deal.totals);
+        let cards = deal.cards.unwrap();
+        assert_eq!(19, cards.a);
+        assert_eq!(21, cards.b);
+        let trick = g.last_trick.unwrap();
+        assert_eq!(3, trick.winner);
+        assert_eq!(4, trick.cards.len());
+    }
+
+    #[test]
+    fn deal_summary_defaults() {
+        let d: DealSummary = serde_json::from_value(json!({
+            "points": {"A": 60, "B": 60},
+            "totals": {"A": 10, "B": 20},
+        }))
+        .unwrap();
+        assert!(!d.patta);
+        assert_eq!(0, d.deal);
+        assert!(d.cards.is_none());
+    }
 }