PlayerController: robust wall-climb hold on thin boards

ProbeWall now falls back to a horizontal multi-sample fan across the capsule
cross-section when the center ray misses, so a thin/narrow board keeps its
grab instead of dropping after wallExitGrace (which stays at 0.15). The
top-out mantle no longer commits on the first probe miss: it requires the
top-edge signature (wall at foot, moving up, headroom clear) to persist for
wallTopOutConfirm (new tunable, default 0.06s) and uses hardened multi-sample
foot/headroom probes, so a transient mid-face miss or a VHACD hull gap no
longer triggers a false mantle.

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

Assets/Prefabs/Player.prefab

@@ -142,6 +142,7 @@ MonoBehaviour:
   wallOffsetReturnSpeed: 2
   wallOffsetFollow: 12
   wallExitGrace: 0.15
+  wallTopOutConfirm: 0.06
   ceilingGrabDistance: 0.02
   wallTopOutBoost: 0.3
   noClimbTag: NoClimb