Add first-person camera mode with pose-aware eye offset and yaw facing

Introduce a FirstPersonController / FirstPersonMode pair (mirroring the
free-cam mode) wired into the GameModeManager Tab cycle. In first person the
mesh is hidden, the eye sits on CameraTarget plus a per-pose
firstPersonCameraTargetYOffset, and the character body yaw is driven to match
the camera via a new single-writer FaceYaw hook on PlayerCharacterController.

Also includes user content edits (poses, prefabs, scene) carried along.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/PlayerPose.cs

@@ -58,6 +58,12 @@ public class PlayerPose : ScriptableObject
              "tracks, without moving the body. Meters.")]
     [SerializeField] private float cameraTargetYOffset;
 
+    [Tooltip("Additional local-up offset applied to the first-person eye (the FirstPersonController's camera " +
+             "position) while this pose is active, on top of the shared camera target. Only affects first " +
+             "person — never the body or the ThirdPersonCamera. Lets a low pose (ball/star) keep its eye at a " +
+             "sensible height even though the camera target sits where third-person frames it. Meters.")]
+    [SerializeField] private float firstPersonCameraTargetYOffset;
+
     /// <summary>Idle clip held while the player stands still in this pose (may be null).</summary>
     public AnimationClip Clip => clip;
 
@@ -87,4 +93,7 @@ public class PlayerPose : ScriptableObject
 
     /// <summary>Local-up offset applied to the camera target while this pose is active (any state).</summary>
     public float CameraTargetYOffset => cameraTargetYOffset;
+
+    /// <summary>Additional local-up offset for the first-person eye, on top of the camera target (first person only).</summary>
+    public float FirstPersonCameraTargetYOffset => firstPersonCameraTargetYOffset;
 }