Add area tactic effects

docs/GODOT_4_6_MIGRATION.md

@@ -48,6 +48,7 @@ powershell -NoProfile -ExecutionPolicy Bypass -File tools\check_godot46_readines
 - A player unit can move, attack, wait, use a tactic, use an item, and equip compatible gear.
 - Movement-triggered supply cache events grant battle inventory items with pickup feedback, and the items persist only after victory.
 - The Threat toggle or `Y` key shows enemy physical and hostile tactic reach, and hovered threatened tiles name the threatening units.
+- Area tactics such as Blaze, Great Mend, and Poison Mist highlight affected cells, apply only to valid targets in the area, and spend MP once per cast.
 - March Order and Hamper Order adjust movement range while active and expire with the normal support/debuff timing.
 - Focus Order and Feint Order adjust physical hit chance through AGI bonuses or penalties and update attack forecasts while active.
 - Poison Mist applies poison, poison ticks at the target team's phase start, and poison defeat immediately ends the battle when it satisfies a victory or defeat condition.