Add game end status with an end_game DM tool and automatic 0-HP detection

Games now have a status/ended_reason pair. The DM can call the new
end_game tool when the story reaches a real conclusion (victory,
defeat, or a resolved one-shot), and the backend independently ends
the game whenever a character's HP drops to 0 or below, regardless of
whether the DM narrates it. The frontend shows a banner and a
"Beendet" badge once a game ends.

HP moves from the freeform combat_stats bag into dedicated
current_hp/max_hp columns on Character, since reliably detecting 0 HP
requires a real integer rather than parsing strings like "3/10" out of
an LLM-authored key/value dict. Also fixed combat_stats to fully
replace on each upsert instead of merging, matching its documented
contract — the merge was leaving stale keys (old HP/TP text) behind
after the model stopped sending them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/llm/tools/character_sheet.py

@@ -32,12 +32,24 @@ TOOL_SCHEMA = {
                 "type": "object",
                 "description": "Ability scores, e.g. {\"STR\": 15, \"DEX\": 12, \"CON\": 14, \"INT\": 10, \"WIS\": 8, \"CHA\": 13}",
             },
+            "current_hp": {
+                "type": "integer",
+                "description": (
+                    "Current hit points. Always send this together with max_hp whenever HP changes "
+                    "(damage, healing, character creation) — the server uses it to detect when a "
+                    "character goes down. Do NOT also put HP/TP in combat_stats, this is the only place for it."
+                ),
+            },
+            "max_hp": {
+                "type": "integer",
+                "description": "Maximum hit points. Send together with current_hp.",
+            },
             "combat_stats": {
                 "type": "object",
                 "description": (
-                    "Key/value readouts, e.g. {\"HP\": \"13/13\", \"RK\": \"19\", \"Initiative\": \"+1\", "
-                    "\"Tempo\": \"7,5 m\", \"Übungsbonus\": \"+2\"}. Send the full current set each time — "
-                    "this replaces whatever was stored before."
+                    "Key/value readouts EXCLUDING hit points (use current_hp/max_hp for those), e.g. "
+                    "{\"RK\": \"19\", \"Initiative\": \"+1\", \"Tempo\": \"7,5 m\", \"Übungsbonus\": \"+2\"}. "
+                    "Send the full current set each time — this replaces whatever was stored before."
                 ),
             },
             "abilities": {
@@ -108,7 +120,11 @@ async def upsert(session: AsyncSession, game_id: uuid.UUID, tool_input: dict) ->
     if "stats" in tool_input and tool_input["stats"] is not None:
         character.stats = {**(character.stats or {}), **tool_input["stats"]}
     if "combat_stats" in tool_input and tool_input["combat_stats"] is not None:
-        character.combat_stats = {**(character.combat_stats or {}), **tool_input["combat_stats"]}
+        character.combat_stats = tool_input["combat_stats"]
+    if "current_hp" in tool_input and tool_input["current_hp"] is not None:
+        character.current_hp = tool_input["current_hp"]
+    if "max_hp" in tool_input and tool_input["max_hp"] is not None:
+        character.max_hp = tool_input["max_hp"]
     if "abilities" in tool_input and tool_input["abilities"] is not None:
         character.abilities = tool_input["abilities"]
     if "equipment" in tool_input and tool_input["equipment"] is not None:
@@ -122,4 +138,9 @@ async def upsert(session: AsyncSession, game_id: uuid.UUID, tool_input: dict) ->
     await session.commit()
     await session.refresh(character)
 
-    return {"character_id": str(character.id), "name": character.name}
+    return {
+        "character_id": str(character.id),
+        "name": character.name,
+        "current_hp": character.current_hp,
+        "max_hp": character.max_hp,
+    }

backend/app/llm/tools/end_game.py

@@ -0,0 +1,40 @@
+import uuid
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.game import Game
+
+TOOL_SCHEMA = {
+    "name": "end_game",
+    "description": (
+        "Call when the story reaches a real conclusion — the party wins, loses, or a one-shot's "
+        "plot is resolved. Marks the game as ended so players see a clear ending. Do not call this "
+        "just because a scene ends; only for a genuine story conclusion."
+    ),
+    "parameters": {
+        "type": "object",
+        "properties": {
+            "reason": {
+                "type": "string",
+                "description": (
+                    "A short narrative summary of how/why the story ended (victory, defeat, or "
+                    "resolution), shown to the players, e.g. 'Das Dorf ist gerettet, die Kerze brennt wieder.'"
+                ),
+            },
+        },
+        "required": ["reason"],
+    },
+}
+
+
+async def end(session: AsyncSession, game_id: uuid.UUID, tool_input: dict) -> dict:
+    game = await session.get(Game, game_id)
+    if game is None:
+        raise ValueError(f"Game {game_id} not found")
+
+    if game.status != "ended":
+        game.status = "ended"
+        game.ended_reason = tool_input["reason"]
+        await session.commit()
+
+    return {"status": "ended", "reason": game.ended_reason}