Enhance runtime targeting logic and add unit tests for target switching and loss conditions

src/runtime-three/runtime-host.ts

@@ -329,6 +329,9 @@ const DIALOGUE_PARTICIPANT_RESTORE_EPSILON_DEGREES = 0.5;
 const TARGETING_LUX_FOLLOW_RATE = 8;
 const TARGETING_LUX_BOB_RATE = 4.2;
 const TARGETING_LUX_PULSE_RATE = 6.5;
+const TARGETING_SIDE_SWITCH_YAW_THRESHOLD_RADIANS = (12 * Math.PI) / 180;
+const TARGETING_CANCEL_YAW_THRESHOLD_RADIANS = (60 * Math.PI) / 180;
+const TARGETING_MAX_ACTIVE_TARGET_DISTANCE = 35;
 // Proposed-target camera nudging is intentionally disabled for now. Lux alone
 // should communicate proposal without moving the gameplay camera.
 // const PROPOSED_TARGET_CAMERA_ASSIST_STRENGTH = 0.28;
@@ -369,6 +372,13 @@ function lerpScalar(start: number, end: number, t: number) {
   return start + (end - start) * t;
 }
 
+function distanceBetweenPoints(
+  left: { x: number; y: number; z: number },
+  right: { x: number; y: number; z: number }
+) {
+  return Math.hypot(left.x - right.x, left.y - right.y, left.z - right.z);
+}
+
 function smoothStep01(value: number) {
   const t = clampScalar(value, 0, 1);