[docs-infra] Multi-tab demo component improvements

Pre-v1:

• Skipping demos without being editable https://github.com/mui/material-ui/issues/41585
• Skipping non React components in visual regressions (Material UI, Base UI, MUI X) https://github.com/mui/material-ui/issues/41584
• eslintrc root

For v1:

• TypeScript support
• Atomic commit for state change

For v1.5

• Fix Code Tabs overflow https://github.com/mui/material-ui/pull/42913
• Fix CodeSandbox/StackBlitz demos: https://github.com/mui/material-ui/issues/42733
• Fix JavaScript demos conversion of tabs: https://github.com/mui/mui-x/pull/13859#issuecomment-2234480917

For v2:

• Editable tabs

    const codes = [tab1Code, tab2Code];
    const scope = withFiles(baseScope, tab1Code, tab2Code).
  

  withFiles from https://github.com/nihgwu/react-runner/blob/974ebc932db7b7c7d59f1b50a79aed705efbf75a/website/src/components/MultiFilesExample/index.tsx#L27.

• Allow using custom labels (default to filename) for imported files, instead of entire relative path
  https://github.com/mui/material-ui/pull/42913#issuecomment-2225904134

For v3

• TS/JS switch using useTransition

Originally posted by @oliviertassinari in https://github.com/mui/material-ui/pull/40901#pullrequestreview-1930884292

Search keywords:

Start by reviewing the remaining unchecked items and the referenced react-runner MultiFilesExample entry point. Determine the scope for editable tabs and the TS/JS switch using useTransition, then check the surrounding docs-infra implementation. Done means both listed v2 and v3 improvements are implemented and their demos behave as intended.