fix(map): load_map rejects two deployment sides bound to the same zone letter (build_states resets its placed set per side, so shared letters deployed camps on top of each other) - fail-fast MapValidationError + README rule, reject/accept tests

README.md

@@ -136,6 +136,9 @@ Règles de construction d'une rencontre :
 - Les combattants d'un camp remplissent les cases de leur zone dans l'ordre
   (ligne, colonne). Une zone trop petite pour le nombre de combattants est une
   erreur.
+- Chaque camp du déploiement doit être lié à une lettre de zone **distincte** :
+  deux camps partageant la même lettre se déploieraient l'un sur l'autre, ce
+  qui est une erreur de carte (`share zone letters`).
 
 ## Interpréter le rapport
 

src/pf1e_simulator/map.py

@@ -140,6 +140,14 @@ def _check_deployment(
     if missing:
         msg = f"deployment zones absent from zones layer: {missing}"
         raise MapValidationError(path, msg)
+    letters = list(deployment.values())
+    shared = sorted({letter for letter in letters if letters.count(letter) > 1})
+    if shared:
+        msg = (
+            "deployment sides share zone letters (each side needs its own "
+            f"distinct zone, or they deploy on top of each other): {shared}"
+        )
+        raise MapValidationError(path, msg)
 
 
 def load_map(path: Path) -> MapSpec:

tests/test_map.py

@@ -109,3 +109,20 @@ def test_rejects_deployment_without_zone(tmp_path: Path) -> None:
     body = _minimal_map() + "zones: |\n  ...\n  .A.\n  ...\ndeployment:\n  players: B\n"
     with pytest.raises(MapValidationError):
         load_map(_write(tmp_path, body))
+
+
+def test_rejects_shared_deployment_zone_letter(tmp_path: Path) -> None:
+    """Two sides bound to the same zone letter would deploy on top of each
+    other (build_states resets its placed set per side): a data error."""
+    body = _minimal_map() + (
+        "zones: |\n  ...\n  .A.\n  ...\ndeployment:\n  players: A\n  monsters: A\n"
+    )
+    with pytest.raises(MapValidationError, match="share zone letters"):
+        load_map(_write(tmp_path, body))
+
+
+def test_accepts_distinct_deployment_zone_letters(tmp_path: Path) -> None:
+    body = _minimal_map() + (
+        "zones: |\n  ...\n  AB.\n  ...\ndeployment:\n  players: A\n  monsters: B\n"
+    )
+    assert load_map(_write(tmp_path, body)).deployment == {"players": "A", "monsters": "B"}