Add see-through X-ray reveal overlay for players

Add a second, additive HDR emission color (_XRayColor) that reveals a
player through walls as a pulsing energy glow, driven during matches:

- Shader: XRayOverlay pass (ZTest Greater, additive) for occluded parts
  plus a matching additive term in the forward fragment for visible
  parts, so the glow shows everywhere and never double-blends. Exposes
  _XRayColor, _XRayPulseSpeed and _XRayPulseStrength for a breathing pulse.
- Render it after opaques via a RenderObjects feature (custom XRayReveal
  light-mode tag) on both PC and Mobile renderers, so the through-wall
  test is depth-sort independent and no longer drops out at some camera
  angles/distances.
- MeshPainter drives _XRayColor alpha through a framerate-independent
  fade (xrayFadeDuration) rather than a hard toggle.
- Reveal is driven per avatar on every client: all remaining un-found
  hiders glow during the Resolution phase, and a hider whose
  ConcealmentMeter EmbeddedPercent exceeds MatchManager.embeddedRevealPercent
  glows via an owner-authoritative NetworkVariable.

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

Assets/Scripts/MatchManager.cs

@@ -145,11 +145,23 @@ public class MatchManager : MonoBehaviour
     [Min(0f)]
     [SerializeField] private float shootCooldown = 0.4f;
 
+    [Header("Concealment reveal")]
+    [Tooltip("A hider whose ConcealmentMeter EmbeddedPercent reaches this value (while a match is running) is " +
+             "revealed through walls with the material's X-ray glow, so nobody can hide by burying itself deep " +
+             "inside geometry. 0..100; 100 effectively disables it (never reached). Read owner-side per avatar.")]
+    [Range(0f, 100f)]
+    [SerializeField] private float embeddedRevealPercent = 80f;
+
     /// <summary>Range of the hunter's shoot raycast (read by <see cref="FirstPersonMode"/>).</summary>
     public float ShootRange => shootRange;
     /// <summary>Hunter shoot cooldown in seconds (read by <see cref="FirstPersonMode"/>).</summary>
     public float ShootCooldown => shootCooldown;
 
+    /// <summary>EmbeddedPercent [0..100] a hider must reach for the through-walls X-ray reveal to switch on
+    /// (only while a match is running). Read by each owner's <see cref="NetworkPlayerSetup"/> against its own
+    /// concealment meter; baked identically on every client, so it needs no replication.</summary>
+    public float EmbeddedRevealPercent => embeddedRevealPercent;
+
     /// <summary>Server-local phase guard. Not replicated - see class summary.</summary>
     public MatchPhase Phase { get; private set; } = MatchPhase.Lobby;