[docs] Fix toolbar anatomy and styled component example closing tags

[CiscoFran10]

• I have followed (at least) the PR section of the contributing guide.

Fixes incorrect closing tags in documentation code blocks.

Changes

Toolbar anatomy

• Fix: <Toolbar.Group> was closed with the self-closing <Toolbar.Group /> instead of </Toolbar.Group>.
• The anatomy now correctly closes the group after the two <Toolbar.Button /> children.

Styling handbook – CSS-in-JS example

• Fix: Closing tags in the styled components (Emotion) example were in the wrong order.
• Replaced the incorrect order with: </StyledMenuPopup> → </StyledMenuPositioner> → </Menu.Portal> so the JSX nesting is correct.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@4307
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@4307
  

commit: 2100a50

[mui-bot]

Bundle size report

Bundle	Parsed size	Gzip size
@base-ui/react	0B(0.00%)	0B(0.00%)

Details of bundle changes

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