fix(material/radio): use default cursor for disabled radios

[NeOMakinG]

Summary:

• Set disabled MDC radio wrappers to use the default cursor.
• Added a regression test for disabled radio indicators in single-selection lists.

Verification:

• Reproduced the issue with a focused browser test that reported pointer for the disabled single-selection radio cursor.
• After the fix the focused list browser test passes in Chromium and Firefox, radio unit tests pass in Chromium and Firefox, the list and radio Bazel build targets pass, and changed files are formatted.

Fixes #31937

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