Fixing docs warnings and docstring updates

[wathen]

Summary

Made the documentation build warning-free and aligned warning policy across build environments.

• Fixed remaining Sphinx/docutils/MyST warnings in API docs and cookbook documentation.
• Removed broad warning suppression from conf.py.
• Enabled Google-style docstring parsing with Napoleon.
• Set Read the Docs to fail on warnings.
• Disabled TODO output in published docs and removed visible placeholder TODOs.
• Verified all cookbook pages, notebooks, images, and local links are present in the built docs.

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Related issue

Closes #41

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Type of change

Select all that apply:

• [ x] Bug fix
• New feature
• Code port
• Refactor
• [ x] Documentation update
• Test update
• [x ] Build / CI change
• Other: <describe>

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