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.

README.md

@@ -1,14 +1,16 @@
 # tavolo
 
-A platform for multiplayer card games. The first game is **scopone
-scientifico** — the four-player, fixed-partnership Italian card game:
+A platform for multiplayer card games. Two games are included:
+**scopone scientifico** — the four-player, fixed-partnership Italian card
+game — and **briscola**, in its classic two-player and four-player
+partnership (*briscola a quattro*) variants:
 
 - **`server/`** — backend: Python + [kaya](https://github.com/woggioni/kaya)
   framework, OIDC login, live games in Redis, match statistics in Postgres.
-  A monorepo of three distributions sharing the `tavolo` namespace: the
-  game-independent `tavolo-platform`, the scopone game `tavolo-scopone`,
-  and the `tavolo-app` composition root wiring them together.
-  See [server/README.md](server/README.md).
+  A monorepo of four distributions sharing the `tavolo` namespace: the
+  game-independent `tavolo-platform`, the `tavolo-scopone` and
+  `tavolo-briscola` games, and the `tavolo-app` composition root wiring
+  them together. See [server/README.md](server/README.md).
 - **`web/`** — frontend: Rust + [Sycamore](https://sycamore.dev) compiled to
   WebAssembly, built with [Trunk](https://trunkrs.dev) and styled with
   [Bootstrap](https://getbootstrap.com) 5.3 (MIT, vendored under
@@ -37,29 +39,29 @@ echo "127.0.0.1 mockoauth" | sudo tee -a /etc/hosts
 ## Between hands
 
 When a hand ends but the match is not decided, the game pauses on a
-**scoring summary screen**: every player sees how each category was won
+**scoring summary screen**: scopone players see how each category was won
 (carte, denara, settebello, primiera, scope — plus napola and asso
-pigliatutto when enabled)
-with the running totals and
-must click "Understood" before the next hand is dealt. If someone is away
-the next hand is dealt automatically after `HAND_ACK_TIMEOUT_SECONDS`
-(default 30s). The match-ending hand is explained on the final screen.
+pigliatutto when enabled), briscola players see the deal's points and any
+*patta*; both see the running totals and must click "Understood" before
+the next hand is dealt. If someone is away the next hand is dealt
+automatically after `HAND_ACK_TIMEOUT_SECONDS` (default 30s). The
+match-ending hand is explained on the final screen.
 
 ## On your turn
 
 Every turn shows a countdown (`TURN_TIMEOUT_SECONDS`, default 30s). If a
 player does not move — disconnected or fallen asleep — the server plays a
-random legal card for them (randomizing among the legal captures when the
+random legal card for them (choosing among the legal captures when the
 rules require a capture), so one absent player cannot stall the table.
 
 ## Watching
 
 Anyone who has the game URL (`/game/<id>`) can watch, logged in or not:
-spectators see the table, the score and every player's captured cards and
-scope, but never a hand and never the join code. The "Copy watch link"
-button in the waiting room and in the game HUD copies the URL to share.
-A spectator who opens the URL before the match starts sees a "game not
-started yet" waiting room.
+spectators see the table, the score and every player's captured cards
+(and scope for scopone), but never a hand and never the join code. The
+"Copy watch link" button in the waiting room and in the game HUD copies
+the URL to share. A spectator who opens the URL before the match starts
+sees a "game not started yet" waiting room.
 
 ## Development
 
@@ -69,10 +71,11 @@ Backend (from `server/`):
 cd server
 python3 -m venv .venv
 .venv/bin/pip install -r requirements.txt
-.venv/bin/pip install -e ./packages/tavolo-platform -e ./packages/tavolo-scopone -e './packages/tavolo-app[dev]'
+.venv/bin/pip install -e ./packages/tavolo-platform -e ./packages/tavolo-scopone -e ./packages/tavolo-briscola -e './packages/tavolo-app[dev]'
 .venv/bin/python -m unittest discover -s tests -t .
 .venv/bin/python -m unittest discover -s packages/tavolo-platform/tests
 .venv/bin/python -m unittest discover -s packages/tavolo-scopone/tests
+.venv/bin/python -m unittest discover -s packages/tavolo-briscola/tests
 ```
 
 Frontend (from `web/`), with the backend running on :8080: