Fix wrench transformer namespace test flake (backport #2492)

[mergify]

Summary

Fix the flaky wrench transformer namespace tests by replacing timing-sensitive, one-shot ROS graph checks with bounded polling.

Changes

• Add a test helper that waits for a publisher on an exact topic using the ROS graph API.
• Update the root-namespace and custom-namespace tests to use bounded polling.
• Preserve the existing topic-name assertions.
• Keep the change limited to test code; no production behavior is modified.

Testing

• colcon build --symlink-install --packages-up-to force_torque_sensor_broadcaster --cmake-args -DBUILD_TESTING=ON

• colcon test --packages-select force_torque_sensor_broadcaster --event-handlers console_cohesion+

• colcon test-result --verbose

• Repeated both namespace tests 100 times:

  • TestWrenchTransformer.NamespaceNormalizationRootNamespace
  • TestWrenchTransformer.NamespaceNormalizationCustomNamespace

• pre-commit run --files force_torque_sensor_broadcaster/test/test_wrench_transformer.cpp

• git diff --check

Results:

• 35 package tests
• 0 errors
• 0 failures
• 0 skipped
• 100 repeated namespace-test iterations passed
• All applicable pre-commit checks passed

Closes #2487

AI assistance

Claude Code assisted with analyzing and preparing the narrowly scoped test change. I manually reviewed the complete diff and verified the build, package tests, repeated stress tests, formatting, lint, and whitespace-check results.

---

This is an automatic backport of pull request #2492 done by [Mergify](https://mergify.com).

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[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.91%. Comparing base (4139208) to head (ef03b6b).
⚠️ Report is 3 commits behind head on kilted.

Files with missing lines	Patch %	Lines
...ensor_broadcaster/test/test_wrench_transformer.cpp	33.33%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           kilted    #2495      +/-   ##
==========================================
- Coverage   86.92%   86.91%   -0.02%     
==========================================
  Files         156      156              
  Lines       15583    15577       -6     
  Branches     1340     1339       -1     
==========================================
- Hits        13545    13538       -7     
- Misses       1568     1571       +3     
+ Partials      470      468       -2     

Flag	Coverage Δ
unittests	86.91% <33.33%> (-0.02%)	⬇️

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

Files with missing lines	Coverage Δ
...ensor_broadcaster/test/test_wrench_transformer.cpp	91.80% <33.33%> (+0.17%)	⬆️

... and 1 file with indirect coverage changes

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