Add painted-height HUD sliders for AO shift and relief intensity

Wire three material-backed look sliders (occlusion AO shift, relief normal
intensity, parallax intensity) through the paint HUD, its layout/state
persistence, the .paint slot format (bumped to v4), owner-authoritative
network sync and the runtime reset, mirroring the existing camo-knob path so
they save, restore, replicate and reset alongside the brush values.

Change the occlusion AO mapping from a division threshold to a linear shift:
AO fades from 1 down to (1 - shift) at the deepest painted hole, so a 0 shift
no longer leaves black spots. Enable _NORMALMAP alongside _PARALLAXMAP so URP
transforms the painted relief normal into world space (otherwise it discards
normalTS and the relief is invisible), and pin the added keyword in the build
keep-alive material.

Stop the pipette from picking the occlusion/height value and turn its toggle
off after a pick. Default the knobs to 0.2 shift / 1.4 normal / 1.0 parallax
across the shader, painter, network and HUD fallbacks.

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

Assets/Scripts/PaintHud.Library.cs

@@ -251,8 +251,9 @@ public partial class PaintHud
     {
         if (!painter || !painter.LoadPaintByName(name)) return;
 
-        // The load also restored the slot's emission intensity + camo knobs onto the painter (v3 slots) ->
-        // push them into the sliders so the HUD reflects the loaded look, exactly like a pipette pick does.
+        // The load also restored the slot's material scalars onto the painter (emission + camo from v3,
+        // the painted-height knobs from v4) -> push them into the sliders so the HUD reflects the loaded
+        // look, exactly like a pipette pick does. SyncCamoSliders covers the camo + height sliders.
         SyncFromPainter();
         SyncCamoSliders();