feat: ban __new__

[paul-nechifor]

Contribution path

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

Problem

• We keep getting tests which use object.__new__(SomeClass) instead of using SomeClass(). This is usually to avoid calling __init__. But not calling __init__ indicates a problem. Either we unnecessary leave __init__ uncovered, or __init__ cannot be ordinarily called because of the bad API design it uses.
• It also means __init__ is often duplicate it test code. This will rarely be updated as the real __init__ is changed.

Solution

• Add a test which bans the use of __new__.

How to Test

AI assistance

Checklist

• This PR is scoped to one issue or clearly stated problem.
• I ran the relevant checks (uv run pytest, pre-commit) for the files I changed.
• I have reviewed and understood every line in this PR.
• I disclosed AI assistance above.
• I have read and approved the CLA.

[greptile-apps]

Greptile Summary

This PR adds a guard against test-side __new__ construction and updates affected tests to use normal object lifecycles.

• Adds an AST-based __new__ check for test files.
• Uses real MCP, odometry, LCM, and MuJoCo module construction.
• Adds cleanup for constructor-backed test fixtures.
• Moves odometry mount rotation setup into initialization.

Confidence Score: 5/5

This looks safe to merge after closing the __new__ guard bypass.

• Normal constructor paths and cleanup behavior are preserved in the updated tests.
• The new AST rule misses calls made through a locally aliased __new__ method.

dimos/codebase_checks/test_no_dunder_new.py

Important Files Changed

Filename	Overview
dimos/codebase_checks/test_no_dunder_new.py	Adds an AST check for explicit __new__ calls in test and conftest files.
dimos/agents/mcp/test_mcp_client_unit.py	Constructs real MCP clients under mocked HTTP and stops them after each test.
dimos/navigation/nav_3d/mls_planner/odom_body_frame.py	Initializes the mount rotation inverse after base configuration construction.
dimos/navigation/nav_3d/mls_planner/test_odom_body_frame.py	Uses real module ports and cleanup in odometry output tests.
dimos/protocol/service/test_lcmservice.py	Exercises service state restoration through actual pickle round-tripping.
dimos/simulation/engines/test_mujoco_sim_module.py	Uses initialized simulation modules and provides required fake-resource cleanup methods.

_{Reviews (1): Last reviewed commit: "feat: ban `__new__`" | Re-trigger Greptile}

[codecov]

Codecov Report

❌ Patch coverage is 69.23077% with 36 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
dimos/simulation/engines/test_mujoco_sim_module.py	55.55%	28 Missing ⚠️
dimos/codebase_checks/test_no_dunder_new.py	74.19%	4 Missing and 4 partials ⚠️

@@            Coverage Diff             @@
##             main    #3009      +/-   ##
==========================================
+ Coverage   72.32%   72.35%   +0.03%     
==========================================
  Files        1023     1024       +1     
  Lines       92004    92038      +34     
  Branches     8412     8420       +8     
==========================================
+ Hits        66541    66595      +54     
+ Misses      23197    23171      -26     
- Partials     2266     2272       +6     

Flag	Coverage Δ
OS-ubuntu-24.04-arm	65.39% <69.23%> (+0.03%)	⬆️
OS-ubuntu-latest	67.74% <69.23%> (+0.03%)	⬆️
Py-3.10	67.73% <69.23%> (+0.03%)	⬆️
Py-3.11	67.73% <69.23%> (+0.03%)	⬆️
Py-3.12	67.73% <69.23%> (+0.03%)	⬆️
Py-3.13	67.73% <69.23%> (+0.02%)	⬆️
Py-3.14	67.73% <69.23%> (+0.03%)	⬆️
Py-3.14t	67.74% <69.23%> (+0.04%)	⬆️
SelfHosted-Large	30.11% <14.52%> (-0.01%)	⬇️
SelfHosted-Linux	37.36% <14.52%> (-0.01%)	⬇️
SelfHosted-macOS	36.23% <14.52%> (-0.01%)	⬇️

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

Files with missing lines	Coverage Δ
dimos/agents/mcp/test_mcp_client_unit.py	91.50% <100.00%> (-0.39%)	⬇️
...s/navigation/nav_3d/mls_planner/odom_body_frame.py	92.59% <100.00%> (+5.09%)	⬆️
...igation/nav_3d/mls_planner/test_odom_body_frame.py	100.00% <100.00%> (ø)
dimos/protocol/service/test_lcmservice.py	100.00% <100.00%> (ø)
dimos/codebase_checks/test_no_dunder_new.py	74.19% <74.19%> (ø)
dimos/simulation/engines/test_mujoco_sim_module.py	66.50% <55.55%> (+0.51%)	⬆️

... and 4 files with indirect coverage changes

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