Add CSS var() hovers when using v4

[thecrypticace]

This adds support for hovering over things like var(--color-red-500) or var(--breakpoint-xl) and showing the value from the theme like we already support with the theme() function.

Additionally, I've improved the hovers for v4 theme keys. They now appear in a @theme block like you'd see them in your CSS and are also syntax highlighted.

Before:

After:

[Copilot]

Pull Request Overview

This PR adds support for CSS var() hovers when using v4. It enhances the hovers by detecting CSS custom property calls (var()) and displaying the corresponding theme value inside a CSS @theme block with syntax highlighting.

• Updated CHANGELOG with var() hover support and improved hover formatting.
• Extended helper matching and type definitions in state and find modules.
• Modified hoverProvider and diagnostics to accommodate var() hovers and added relevant tests in the hover test suite.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/vscode-tailwindcss/CHANGELOG.md	Updated changelog with information about var() hover support and improved @theme hover output.
packages/tailwindcss-language-service/src/util/state.ts	Added 'var' as a valid helper type.
packages/tailwindcss-language-service/src/util/find.ts	Extended regex to detect 'var' helper and updated type handling.
packages/tailwindcss-language-service/src/hoverProvider.ts	Added conditional logic to format var() hovers in a CSS @theme block.
packages/tailwindcss-language-service/src/diagnostics/getInvalidConfigPathDiagnostics.ts	Skips validation for var() helper functions.
packages/tailwindcss-language-server/tests/hover/hover.test.js	Added tests to verify the hover output for var() and theme calls.

Comments suppressed due to low confidence (1)

packages/tailwindcss-language-server/tests/hover/hover.test.js:559

• [nitpick] The test name 'wip' is ambiguous; consider using a more descriptive name to clearly indicate the test scenario being validated.

  name: 'wip',

[thecrypticace]

Copilot you could at least have the decency to wrap at-rule names in backticks 🤦‍♂️