fix(skills): eliminate idle hydra turret inward crossfire self-targeting (Ref #399)

- Remove targetX and targetY from stationary turret projectile definition in castSkill (act-scene.ts)
- Remove idle fallback to projectile.targetX/Y in tickProjectiles (skills.ts) so turrets only fire when an alive target is found within range
- Add negative unit test in Dimension 3 verifying 0 projectiles are spawned over 50 ticks with empty targets array

src/game/skills.ts

@@ -2713,11 +2713,6 @@ export function tickProjectiles(
           }
         }
 
-        if (targetX === undefined && projectile.targetX !== undefined && projectile.targetY !== undefined) {
-          targetX = projectile.targetX
-          targetY = projectile.targetY
-        }
-
         if (targetX !== undefined && targetY !== undefined) {
           const dx = targetX - x
           const dy = targetY - y

src/scene/act-scene.ts

@@ -1350,8 +1350,6 @@ export function castSkill(
         isTurret: true,
         fireCadenceTicks: 25,
         headIndex: i,
-        targetX,
-        targetY,
         spawnMissileType: 'hydra',
         pierce: false,
       })

tests/hydra-missile-113c.test.ts

@@ -249,6 +249,38 @@ describe('[Skill #062] Hydra — 7-Dimensional 1.13c Verification Suite (Issue #
       // Target was enemyA
       expect(spawned[0]!.vy).toBeCloseTo(16, 0.1)
     })
+
+    it('spawns exactly 0 projectiles over 50 ticks when targets array is empty (idle turret parity)', () => {
+      const turret: Projectile = {
+        skillId: '62',
+        x: 100,
+        y: 100,
+        vx: 0,
+        vy: 0,
+        damage: 35,
+        ttl: 250,
+        fromPlayer: true,
+        missileType: 'hydra_turret',
+        isTurret: true,
+        fireCadenceTicks: 25,
+        spawnMissileType: 'hydra',
+        targetX: 100,
+        targetY: 100,
+      }
+
+      let current: readonly Projectile[] = [turret]
+      const spawnedBolts: Projectile[] = []
+
+      for (let tick = 1; tick <= 50; tick++) {
+        const res = tickProjectiles(current, [], { overlap: () => 0 })
+        if (res.spawnedProjectiles && res.spawnedProjectiles.length > 0) {
+          spawnedBolts.push(...res.spawnedProjectiles)
+        }
+        current = res.alive.filter(p => p.isTurret)
+      }
+
+      expect(spawnedBolts.length).toBe(0)
+    })
   })
 
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