Add NoClimb climb filter and kill-plane rescue to player controller

Two player-controller additions:

NoClimb: colliders tagged "NoClimb" are now invisible to wall-climb and
ceiling-grab. The grab detector (OnControllerColliderHit) and all three
climb probes (ProbeWall, ProbeCeiling, WallInFront) skip them, so such a
surface still blocks the capsule physically but can never be grabbed,
re-probed onto, or treated as a ceiling. WalkableGroundBelow is left
untouched (it only accepts walkable ground). The tag is read from a
serialized field (default "NoClimb"); an empty tag disables the check.

Rescue: a kill-plane fail-safe. The owner captures its spawn point on the
first Update frame (after OnNetworkSpawn's ring offset has landed) and,
if it falls below rescueMinY (-100), teleports back there with all
momentum cleared, toggling the CharacterController around the write like
PlaceOnSpawnRing. Owner-only; the authoritative NetworkTransform
replicates the reset. Runs ahead of the control gate so it rescues in any
mode.

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

Assets/Scripts/PlayerCharacterController.cs

@@ -75,6 +75,12 @@ public class PlayerCharacterController : MonoBehaviour
              "animation. Only while airborne (not grounded, not wall-climbing). Scales with player size.")]
     public float fallAnimationSpeed = 4f;
 
+    [Header("Rescue")]
+    [Tooltip("Kill-plane fail-safe: if the player falls below this world Y (e.g. off the map into the void), " +
+             "they are teleported back to where this avatar spawned (spawn center + per-client ring offset) " +
+             "with all momentum cleared. Owner-only; the authoritative NetworkTransform replicates the reset.")]
+    public float rescueMinY = -100f;
+
     [Header("Slope Sliding")]
     [Tooltip("Slide down surfaces steeper than the CharacterController's Slope Limit instead of balancing on them.")]
     public bool slideDownSteepSlopes = true;
@@ -136,6 +142,9 @@ public class PlayerCharacterController : MonoBehaviour
     [Tooltip("Upward hop when topping out over a wall/slope edge, so holding W carries you onto the ledge instead of dropping back onto the face and re-grabbing. In meters of jump height; 0 = no hop.")]
     public float wallTopOutBoost = 0.3f;
 
+    [Tooltip("Colliders with this tag are invisible to wall-climb and ceiling-grab: they still block the capsule physically, but can never be grabbed, re-probed onto, or used as a ceiling. Leave empty to disable.")]
+    public string noClimbTag = "NoClimb";
+
     [Tooltip("Camera orbit input; paused while dragging the wall-climb offset. Auto-found if empty.")]
     [SerializeField] private ThirdPersonOrbitInput cameraOrbit;
 
@@ -224,6 +233,8 @@ public class PlayerCharacterController : MonoBehaviour
     private bool _movingOnGround;         // snapshot: grounded & moving above the run threshold (exposed via IsMovingOnGround)
     private bool _isFalling;              // snapshot: airborne & descending past the fall threshold (exposed via IsFalling)
     private float _groundOffset;          // signed vertical mesh raise from the ground mouse pose-adjust (+ up / - down); folded into SetMeshLean
+    private Vector3 _spawnPosition;       // world position this avatar spawned at; the rescue (kill-plane) teleport target
+    private bool _spawnCaptured;          // false until the first Update captures the spawn position (after OnNetworkSpawn's ring offset has landed)
 
     // Ground contact normal from the latest Move (for slope sliding).
     private Vector3 _groundNormal = Vector3.up;
@@ -304,6 +315,21 @@ public class PlayerCharacterController : MonoBehaviour
 
     void Update()
     {
+        // Kill-plane fail-safe (owner-only: the controller is disabled on remotes). Capture the spawn
+        // point on the first frame -- by now OnNetworkSpawn's ring offset has landed -- then snap the
+        // player back if they fall through the world. Runs ahead of the control gate so it rescues in
+        // any mode (paint/free-cam included).
+        if (!_spawnCaptured)
+        {
+            _spawnPosition = transform.position;
+            _spawnCaptured = true;
+        }
+        else if (transform.position.y < rescueMinY)
+        {
+            RescueToSpawn();
+            return;
+        }
+
         float h = 0f, v = 0f;
         bool jumpPressed = false;
         bool sprinting = false;
@@ -471,6 +497,24 @@ public class PlayerCharacterController : MonoBehaviour
         _isFalling = !_controller.isGrounded && _verticalVelocity < -fallAnimationSpeed * CapsuleScale;
     }
 
+    /// <summary>
+    /// Kill-plane rescue: snap the avatar back to its captured spawn point and clear all momentum. The
+    /// CharacterController overrides direct transform writes, so it is toggled around the move (same
+    /// pattern as <see cref="NetworkPlayerSetup.PlaceOnSpawnRing"/>). Owner-only; the authoritative
+    /// NetworkTransform replicates the new position to remotes.
+    /// </summary>
+    private void RescueToSpawn()
+    {
+        bool reenable = _controller && _controller.enabled;
+        if (_controller) _controller.enabled = false;
+        transform.position = _spawnPosition;
+        if (_controller) _controller.enabled = reenable;
+
+        _verticalVelocity = 0f;
+        _horizontalVelocity = Vector3.zero;
+        _slideSpeed = 0f;
+    }
+
     /// <summary>
     /// Enters wall-climb mode only when the move input actively pushes into a wall
     /// (not on mere contact). Leaving while climbing is handled in
@@ -950,6 +994,13 @@ public class PlayerCharacterController : MonoBehaviour
     /// </summary>
     private static bool IsPlayerCollider(Collider c) => c.GetComponentInParent<PlayerCharacterController>();
 
+    /// <summary>
+    /// True if the collider is tagged as non-climbable (<see cref="noClimbTag"/>): every climb probe
+    /// and the grab detector skip it, so such a wall/ceiling blocks the capsule but is never grabbed,
+    /// re-probed onto, or treated as a ceiling. Empty/unset tag disables the check (never throws).
+    /// </summary>
+    private bool IsNoClimb(Collider c) => !string.IsNullOrEmpty(noClimbTag) && c && c.CompareTag(noClimbTag);
+
     /// <summary>
     /// Raycasts from the character center toward the surface (along -_wallNormal) to find the
     /// current normal and the gap (surface clearance) to it. The capsule's support distance
@@ -973,7 +1024,7 @@ public class PlayerCharacterController : MonoBehaviour
         bool found = false;
         for (int i = 0; i < count; i++)
         {
-            if (IsPlayerCollider(_wallProbe[i].collider)) // skip self and other player avatars
+            if (IsPlayerCollider(_wallProbe[i].collider) || IsNoClimb(_wallProbe[i].collider)) // skip self, other player avatars, and no-climb surfaces
                 continue;
             if (_wallProbe[i].distance < best)
             {
@@ -1018,7 +1069,7 @@ public class PlayerCharacterController : MonoBehaviour
         bool found = false;
         for (int i = 0; i < count; i++)
         {
-            if (IsPlayerCollider(_wallProbe[i].collider))
+            if (IsPlayerCollider(_wallProbe[i].collider) || IsNoClimb(_wallProbe[i].collider))
                 continue;
             if (_wallProbe[i].normal.y >= CeilingNormalThreshold) // not a ceiling
                 continue;
@@ -1090,7 +1141,7 @@ public class PlayerCharacterController : MonoBehaviour
             origin, -_wallNormal, _wallProbe, maxDist, ~0, QueryTriggerInteraction.Ignore);
         for (int i = 0; i < count; i++)
         {
-            if (IsPlayerCollider(_wallProbe[i].collider))
+            if (IsPlayerCollider(_wallProbe[i].collider) || IsNoClimb(_wallProbe[i].collider))
                 continue;
             return true;
         }
@@ -1198,7 +1249,7 @@ public class PlayerCharacterController : MonoBehaviour
     /// </summary>
     private void OnControllerColliderHit(ControllerColliderHit hit)
     {
-        if (enableWallClimb)
+        if (enableWallClimb && !IsNoClimb(hit.collider))
         {
             float angle = Vector3.Angle(hit.normal, Vector3.up);
             if (angle >= wallMinAngle)