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/Resources/PaintVariantKeepAlive.mat

@@ -27,6 +27,7 @@ Material:
   m_ValidKeywords:
   - _EMISSION
   - _METALLICSPECGLOSSMAP
+  - _NORMALMAP
   - _OCCLUSIONMAP
   - _PARALLAXMAP
   m_InvalidKeywords: []
@@ -47,7 +48,7 @@ Material:
         m_Scale: {x: 1, y: 1}
         m_Offset: {x: 0, y: 0}
     - _BumpMap:
-        m_Texture: {fileID: 0}
+        m_Texture: {fileID: 2800000, guid: c24e49ee8237bac42930ef868a325c48, type: 2}
         m_Scale: {x: 1, y: 1}
         m_Offset: {x: 0, y: 0}
     - _DetailAlbedoMap: