feat(observation): expose spell cast time in the snapshot

The per-spell Observation dict gains the additive cast_time key: the
registry spell's budget code on a hit, "standard" on a miss (mirroring
the engine's resolver fallback), so an LLM policy can schedule casts
against the action budget it sees reported back.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/pf1e_simulator/combat.py

@@ -4574,6 +4574,7 @@ class CombatEngine:
                 "half_on_save": False,
                 "save_negates": False,
                 "area": None,
+                "cast_time": "standard",
             }
         half_on_save = _spell_half_on_save(spell)
         return {
@@ -4587,6 +4588,7 @@ class CombatEngine:
             "half_on_save": half_on_save,
             "save_negates": spell.save != "none" and not half_on_save,
             "area": _spell_area_dict(spell),
+            "cast_time": spell.cast_time,
         }
 
     def _cast_spell(