fix(spells): correct the sound burst save

PF1e (SRD spells/sound-burst.md): "Every creature in the area takes 1d8 points of sonic damage and must succeed on a Fortitude save to avoid being stunned for 1 round" — the Fortitude partial negates the stun only, never the dice. The damage component declared half_on_save: true, halving the sonic damage on a successful save. DamageEffect gains a save_negates flag (default True, existing behavior unchanged); sound_burst.json declares half_on_save: false + save_negates: false so the 1d8 is full regardless while the condition keeps save_negates. README updated.

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

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

src/pf1e_simulator/combat.py

@@ -5534,7 +5534,7 @@ class CombatEngine:
             raw = effect.formula.max_value()
         if saved and effect.half_on_save:
             dmg = max(0, raw // 2)
-        elif saved:
+        elif saved and effect.save_negates:
             dmg = 0
         else:
             dmg = raw