fix(rules): convert bane to a 50-ft enemies-only burst

SRD spells/bane.md: enemies within a 50-ft burst centered on the caster
take a -1 penalty on attack rolls and a -1 penalty on saving throws
against fear effects; Will negates. The -1 penalty is approximated with
the shaken condition (-2), matching the existing Doom approximation.

- bane.json: single-target condition -> AreaEffect burst radius_ft 50,
  targets "enemies", ConditionEffect shaken 10 rounds save_negates
  (range/save kept as medium/will for the registry pin)
- combat.py: _metamagic_transform_sub now copies AreaEffect.targets so
  an Extend Spell on an area spell preserves the allies/enemies filter
- tests: TestBaneEnemiesOnly (enemy in burst debuffed, allies/caster
  unaffected, successful Will save negates)

src/pf1e_simulator/combat.py

@@ -6613,6 +6613,7 @@ class CombatEngine:
                     for sub in effect.effects
                 ),
                 save_for_half=effect.save_for_half,
+                targets=effect.targets,
             )
         return effect