Operator battle voices: the official combat lines play by voice slot during battles, one at a time (#73)

Deploy, skill and result lines come from the operators' official voice slots; a newer line takes the channel over (stale callbacks of the replaced line no longer release it), and the result line is spoken by an operator of the player's own battle. Contributed by @Convey123.

server/sim/ai.js

@@ -155,6 +155,12 @@ export function performAttack(b, u, prof, targets, opts = null) {
   u.stats.attacks++;
   const attackId = ++b._attackSeq; // every damage instance of this attack (all targets, splash, chain) carries it
   const isHeal = !!(prof.heal && prof.dmgType === 'heal');
+  // 首次接敌 (official voice type ENCOUNTER_ENEMY, ≥ 3 s between two such lines): one event the first time a unit
+  // attacks an enemy, whatever the attack is — the client answers with that operator's 行动开始 line (audio.js voice).
+  if (!isHeal && u.side === 'ally' && !u.mem.engaged && targets.some((t) => t && t.side === 'enemy')) {
+    u.mem.engaged = true;
+    b._ev(['engage', u.id]);
+  }
   const ranged = !prof._fortressMelee && prof.attack === 'ranged' && prof.projectile && prof.projectile !== 'none' && prof.projectile !== 'beam';
   const vis = prof._fortressMelee ? 'none' : (prof.projectile || 'none');
   for (let i = 0; i < targets.length; i++) {