docs: fix Sphinx docstring formatting and reST syntax errors

[petercorke]

• Fix LaTeX escaping in docstrings (add missing braces, convert to raw strings)
• Correct reST indentation for documentation lists and notes
• Fix code example imports and function references
• Update cross-references using proper Sphinx format (:meth:, ~seealso:)
• Fix parameter name references in docstrings (S→s, math.pi→np.pi)
• Add missing type annotations in parameter documentation
• Remove obsolete documentation files (classes-2d.rst, classes-3d.rst)
• Improve reference formatting for external links

Fixes 19+ files with sphinx build warnings and documentation clarity issues. All changes are non-functional; improve rendering and consistency only.

[petercorke]

Note that classes-2d/3d.rst, shown as deleted, are orphaned documentation stub files. They were likely used for autodoc generation but are no longer referenced in the main documentation structure (not included in any .rst index or toctree).

[codecov-commenter]

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