fix(rules): document the blocks_los flag as LINE OF EFFECT semantics (SRD aiming-a-spell.md: 'A line of effect is canceled by a solid barrier. It's like line of sight for ranged weapons, except that it's not blocked by fog, darkness, and other factors that limit normal sight') - vision-only concealment terrain is not modeled; concealment rides conditions (miss_chance), not the map

README.md

@@ -221,6 +221,16 @@ optionnel `cover_bonus` (`2`, `4` ou `8`) encode le niveau de couvert PF1e
 (partiel +2, standard +4, amélioré +8) ; `cover: true` sans `cover_bonus`
 vaut couvert standard (+4), idem pour un terrain `blocks_los`.
 
+Sémantique de `blocks_los` — **ligne d'effet, non ligne de vision** (SRD
+« Aiming a Spell — Line of Effect ») : « A line of effect is a straight,
+unblocked path that indicates what a spell can affect. A line of effect is
+canceled by a solid barrier. It's like line of sight for ranged weapons,
+except that it's not blocked by fog, darkness, and other factors that limit
+normal sight. » Le drapeau encode donc une **barrière solide** ; un terrain
+qui ne limite que la vision normale (brouillard, obscurité, dissimulation)
+n'est pas modélisé — le moteur n'a qu'un seul drapeau, et la dissimulation
+passe par les conditions (`miss_chance`), pas par la carte.
+
 ### Monstre (JSON)
 
 ```json