feat(narrative): add world + god mode API endpoints

Six new endpoints under /api/narrative/*:
- GET  /world/<sim_id>                       — full world state
- POST /world/<sim_id>/rules                 — replace rules list
- POST /world/<sim_id>/locations             — upsert location
- POST /godmode/<sim_id>/inject-event        — inject world event
- POST /godmode/<sim_id>/modify-emotion      — overwrite emotions
- POST /godmode/<sim_id>/kill                — kill character

Validation:
- 400 on missing required fields (description, character_id, rules)
- 400 on invalid round (must be non-negative int or null)
- 404 on character not found (from ValueError in handlers)

Smoke-tested via Flask test client — all 11 response codes correct.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/narrative.py

@@ -12,6 +12,12 @@ from ..config import Config
 from ..services.narrative.story_store import StoryStore
 from ..services.narrative.narrative_translator import translate_round
 from ..services.narrative.character_engine import CharacterEngine
+from ..services.narrative.world_state import WorldStateStore
+from ..services.narrative.god_mode import (
+    inject_event as gm_inject_event,
+    modify_emotion as gm_modify_emotion,
+    kill_character as gm_kill_character,
+)
 
 
 def _sim_dir(sim_id: str) -> str:
@@ -80,3 +86,95 @@ def initialize_characters(sim_id):
     engine = CharacterEngine(store)
     characters = engine.initialize_from_profiles(profiles)
     return jsonify({"count": len(characters), "characters": characters})
+
+
+# ---------------------------------------------------------------------------
+# World State endpoints
+# ---------------------------------------------------------------------------
+
+@narrative_bp.route('/world/<sim_id>', methods=['GET'])
+def get_world(sim_id):
+    """Return the full world_state.json for this simulation."""
+    store = WorldStateStore(_sim_dir(sim_id))
+    return jsonify(store.load())
+
+
+@narrative_bp.route('/world/<sim_id>/rules', methods=['POST'])
+def set_rules(sim_id):
+    """Replace the full rules list. Body: {"rules": [str, ...]}."""
+    data = request.get_json() or {}
+    rules = data.get('rules')
+    if not isinstance(rules, list):
+        return jsonify({"error": "rules must be a list of strings"}), 400
+    store = WorldStateStore(_sim_dir(sim_id))
+    store.set_rules([str(r) for r in rules])
+    return jsonify(store.load())
+
+
+@narrative_bp.route('/world/<sim_id>/locations', methods=['POST'])
+def upsert_location(sim_id):
+    """Insert or update a location. Body: {"id", "name", "description"}."""
+    data = request.get_json() or {}
+    if not data.get('id') or not data.get('name'):
+        return jsonify({"error": "id and name are required"}), 400
+    store = WorldStateStore(_sim_dir(sim_id))
+    loc = store.upsert_location({
+        "id": str(data['id']),
+        "name": str(data['name']),
+        "description": str(data.get('description', '')),
+    })
+    return jsonify(loc)
+
+
+# ---------------------------------------------------------------------------
+# God Mode endpoints
+# ---------------------------------------------------------------------------
+
+@narrative_bp.route('/godmode/<sim_id>/inject-event', methods=['POST'])
+def godmode_inject_event(sim_id):
+    """Inject a world event. Body: {"description", "round"? (optional, >=0)}."""
+    data = request.get_json() or {}
+    description = data.get('description')
+    if not description:
+        return jsonify({"error": "description is required"}), 400
+
+    round_num = data.get('round')
+    if round_num is not None:
+        try:
+            round_num = int(round_num)
+            if round_num < 0:
+                raise ValueError()
+        except (TypeError, ValueError):
+            return jsonify({"error": "round must be a non-negative integer"}), 400
+
+    evt = gm_inject_event(_sim_dir(sim_id), description=str(description), round_num=round_num)
+    return jsonify(evt)
+
+
+@narrative_bp.route('/godmode/<sim_id>/modify-emotion', methods=['POST'])
+def godmode_modify_emotion(sim_id):
+    """Overwrite emotion values. Body: {"character_id", "emotions": {name: float}}."""
+    data = request.get_json() or {}
+    char_id = data.get('character_id')
+    emotions = data.get('emotions')
+    if not char_id or not isinstance(emotions, dict):
+        return jsonify({"error": "character_id and emotions are required"}), 400
+    try:
+        char = gm_modify_emotion(_sim_dir(sim_id), str(char_id), emotions)
+    except ValueError as e:
+        return jsonify({"error": str(e)}), 404
+    return jsonify(char)
+
+
+@narrative_bp.route('/godmode/<sim_id>/kill', methods=['POST'])
+def godmode_kill(sim_id):
+    """Mark a character as dead. Body: {"character_id"}."""
+    data = request.get_json() or {}
+    char_id = data.get('character_id')
+    if not char_id:
+        return jsonify({"error": "character_id is required"}), 400
+    try:
+        char = gm_kill_character(_sim_dir(sim_id), str(char_id))
+    except ValueError as e:
+        return jsonify({"error": str(e)}), 404
+    return jsonify(char)