feat: allow fine grain voxels without publishing

[aclauer]

Contribution path

• Small, safe change that does not need a tracking issue
• Linked issue or discussion: DIM-XXX / #XXX / URL

Problem

even if we don't publish the fine grain map from the ray tracer on the transport it reduces clipping in the voxel map

Solution

• allow ray tracer to use fine grain voxels without publishing them
• enforce we only publish fine grain map if voxel divisor > 0

How to Test

AI assistance

Checklist

• I have read and approved the CLA.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
dimos/mapping/ray_tracing/test_voxel_map.py	0.00%	1 Missing ⚠️

@@           Coverage Diff           @@
##             main    #3687   +/-   ##
=======================================
  Coverage   77.78%   77.78%           
=======================================
  Files        1287     1287           
  Lines      123467   123468    +1     
  Branches    10822    10822           
=======================================
+ Hits        96044    96045    +1     
- Misses      24281    24282    +1     
+ Partials     3142     3141    -1     

Flag	Coverage Δ
OS-ubuntu-24.04-arm	72.76% <75.00%> (+<0.01%)	⬆️
OS-ubuntu-latest	74.61% <75.00%> (-0.01%)	⬇️
Py-3.10	74.60% <75.00%> (-0.01%)	⬇️
Py-3.11	74.60% <75.00%> (-0.01%)	⬇️
Py-3.12	74.60% <75.00%> (-0.01%)	⬇️
Py-3.13	74.60% <75.00%> (+<0.01%)	⬆️
Py-3.14	74.61% <75.00%> (+<0.01%)	⬆️
Py-3.14t	74.60% <75.00%> (-0.01%)	⬇️
SelfHosted-Large	29.98% <75.00%> (+<0.01%)	⬆️
SelfHosted-Linux	35.22% <75.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
dimos/mapping/ray_tracing/module.py	100.00% <100.00%> (ø)
dimos/mapping/ray_tracing/test_voxel_map.py	2.75% <0.00%> (ø)

... and 5 files with indirect coverage changes

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