Harden checkpoint reuse and combat validation

internal/modules/dnd/extract/combatturns/assets/prompts/instructions.md

@@ -1,5 +1,7 @@
 Return the combat_turns array even when no combat turn is established. Return
-one or more actions for every turn. Use one of the supported turn_kind and
-action category values. Set round to null when the transcript does not state an
+one or more actions for every turn. For turn_kind, use exactly one of: turn,
+reaction, legendary_action, lair_action, or other. For each action category,
+use exactly one of: attack, spell, movement, item, ability_check, saving_throw,
+condition, or other. Set round to null when the transcript does not state an
 explicit or unambiguous positive round number. Set resolution to null when the
 transcript establishes the declaration but not an immediate resolution.