feat(observation): expose ranged threat grid

tests/test_observation_enriched.py

@@ -1042,8 +1042,9 @@ def test_observation_enriched_e5_existing_keys_preserved() -> None:
     """Given: an Observation built for the L5 fields
     When: the top-level dict is inspected
     Then: all pre-existing top-level keys remain (round, acting_combatant,
-    combatants, pairs, terrain, elevation) and the two new keys
-    (threatened, terrain_semantics) are added — exact key set."""
+    combatants, pairs, terrain, elevation) and the new keys
+    (threatened, ranged_threatened, terrain_semantics,
+    condition_definitions, initiative_order) are added — exact key set."""
     hero = make_combatant("hero")
     foe = make_combatant("foe")
     hero_state = make_state(hero, "players", (0, 0))
@@ -1059,6 +1060,7 @@ def test_observation_enriched_e5_existing_keys_preserved() -> None:
         "terrain",
         "elevation",
         "threatened",
+        "ranged_threatened",
         "terrain_semantics",
         "condition_definitions",
         "initiative_order",