WARNING: html_static_path entry 'source/_static' is placed inside out… (backport #6345)

[mergify]

…dir.

Description

the root cause was never about html_static_path resolution, it was the devcontainer workspace mount point.
with the workspace mounted at /tmp/doc_repository, the sphinx outdir (which defaults to something like /tmp/...) would end up encompassing the source tree. sphinx saw that /tmp/doc_repository/source/_static was inside its output directory and warned about it. by moving the workspace mount to /workspaces/doc_repository (the standard devcontainer convention), the source tree is no longer under /tmp/, so there's no path overlap with sphinx's outdir. and reverting html_static_path back to the simple relative 'source/_static' is the right cleanup since the os.path.abspath() wrapper was never helping.

i confirmed and verified this PR with devcontainer and venv, and there was no warning came up.

fixes #6071
replaces #6341 and #6178

Did you use Generative AI?

No

Additional Information

This problem only appears on dev container environment.
#6341 and #6178 tries to close it, but never worked AFAIK.

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This is an automatic backport of pull request #6345 done by [Mergify](https://mergify.com).

[github-actions]

HTML artifacts: https://github.com/ros2/ros2_documentation/actions/runs/24070988912/artifacts/6301418300.

To view the resulting site:

1. Click on the above link to download the artifacts archive
2. Extract it
3. Open html-artifacts-6349/index.html in your favorite browser