Add poison damage over time tactics

tools/validate_data.ps1

@@ -100,7 +100,7 @@ $validBonusStats = @("hp", "mp", "atk", "def", "int", "agi")
 $validSkillKinds = @("damage", "heal", "support")
 $validSkillTargets = @("enemy", "ally", "self", "any")
 $validSkillStats = @("atk", "def", "int", "agi")
-$validSkillEffectTypes = @("stat_bonus")
+$validSkillEffectTypes = @("stat_bonus", "damage_over_time")
 $validDialogueSides = @("left", "right")
 $validPortraitPathPattern = '^res://.+\.(png|jpg|jpeg|webp)$'
 $knownFlagIds = New-Object System.Collections.Generic.HashSet[string]
@@ -773,6 +773,17 @@ function Check-Skill-Definitions() {
                 if ([int](Get-Prop $effect "duration_turns" 1) -le 0) {
                     Fail "Skill $skillId stat_bonus effect must have positive duration_turns."
                 }
+            } elseif ($effectType -eq "damage_over_time") {
+                $status = [string](Get-Prop $effect "status" "")
+                if ([string]::IsNullOrWhiteSpace($status) -or -not ($status -match '^[a-z0-9_]+$')) {
+                    Fail "Skill $skillId damage_over_time effect must have a stable status."
+                }
+                if ([int](Get-Prop $effect "amount" 0) -le 0) {
+                    Fail "Skill $skillId damage_over_time effect must have positive amount."
+                }
+                if ([int](Get-Prop $effect "duration_turns" 1) -le 0) {
+                    Fail "Skill $skillId damage_over_time effect must have positive duration_turns."
+                }
             }
         }
     }