Implement the world-state summarization from the Phase 2 plan

Context was pure full-text replay of every message, capped at 40k
chars with oldest-dropped-first — no summarization/world-state layer,
as called out as still-missing in an earlier conversation.

Add a new update_world_state DM tool that persists a compact,
DM-authored recap (key NPCs, current location, open plot threads,
party/inventory state) to a new world_state table, one row per game.
It's injected into the system prompt every turn, ahead of the raw
message window. The DM is instructed to call it regularly — at every
scene change or major event, not just at the end — sending the full
current picture each time (matches the replace-not-merge pattern
already used for combat_stats/abilities/equipment).

Since the summary now backs up everything older, shrink the raw
message window from 40k to 16k chars — it's recent continuity now,
not the sole memory of the session. Full history remains available
via "Volltext laden" regardless, since that reads the messages table
directly rather than through this context builder.

Simplified from the original plan sketch (state JSONB) to a single
free-text summary field — natural-language recaps are something an
LLM authors well; a structured world model would need a schema the
DM would have to conform to for no real benefit here.

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

backend/app/llm/orchestrator.py

@@ -9,7 +9,7 @@ from app.config import settings
 from app.llm.client import get_dm_system_prompt, get_llm_client
 from app.llm.context import build_context
 from app.llm.json_utils import fix_double_escaped_unicode
-from app.llm.tools import character_sheet, dice, end_game, monster
+from app.llm.tools import character_sheet, dice, end_game, monster, world_state
 from app.models.game import Game
 from app.models.message import Message
 from app.rag.retrieval import build_rag_block
@@ -24,6 +24,7 @@ TOOLS = [
     {"type": "function", "function": character_sheet.TOOL_SCHEMA},
     {"type": "function", "function": end_game.TOOL_SCHEMA},
     {"type": "function", "function": monster.TOOL_SCHEMA},
+    {"type": "function", "function": world_state.TOOL_SCHEMA},
 ]
 
 
@@ -41,6 +42,8 @@ async def _execute_tool_call(
             return await end_game.end(session, game_id, tool_input)
         if tool_name == "update_monster_hp":
             return await monster.update(session, game_id, tool_input)
+        if tool_name == "update_world_state":
+            return await world_state.update(session, game_id, tool_input)
         return {"error": f"Unknown tool {tool_name!r}"}
     except Exception as exc:  # noqa: BLE001
         logger.warning("Tool call %s failed: %s", tool_name, exc)
@@ -85,6 +88,14 @@ async def run_dm_turn(
             f"Name: {game.name}\nBeschreibung: {game.description}"
         )
 
+    world_summary = await world_state.get_summary(session, game_id)
+    if world_summary:
+        system_prompt = (
+            f"{system_prompt}\n\nBisheriger Weltzustand (von dir zuletzt über update_world_state "
+            f"zusammengefasst — der Chatverlauf unten zeigt nur ein aktuelles Fenster, das hier "
+            f"trägt alles Ältere):\n{world_summary}"
+        )
+
     if latest_player_message:
         rag_block = await build_rag_block(session, latest_player_message)
         if rag_block: