refactor(examples): improve React examples code quality

[liwenka1]

Changes

• Improve variable naming for better readability (rows → rowSizes, columns → columnSizes)
• Remove unused imports and variables (Row type, setData)
• Fix type safety issues (add explicit String() conversion for symbol keys)
• Unify array type syntax to Array<T> for consistency
• Remove unnecessary non-null assertions in makeData.ts
• Clean up eslint-disable comments after fixing underlying issues

Motivation

These changes improve code quality in the React examples, making them easier to understand for developers learning the library. The naming improvements (rowSizes/columnSizes) more clearly indicate that these arrays contain dimension values rather than the actual row/column components.

Testing

• All modified examples tested locally
• No runtime behavior changes
• Lint errors resolved

[changeset-bot]

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Latest commit: a4c736c

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