Remove deprecated `cmkOptions.keyframes` option in the next major release

[mizdra]

#430 deprecated cmkOptions.keyframes in favor of cmkOptions.animation. The old option still works but reports a deprecation warning.

In the next major release, remove cmkOptions.keyframes entirely:

• Remove the option handling and the deprecation warning from the config loader
• Remove the keyframes property from the VS Code tsconfig schema
• Remove the deprecated section from README

🤖 Generated with Claude Code