Allow-list .gitignore breaks Tailwind CSS v4 @source scanning for vendor/

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The `.gitignore` in this repository uses an allow-list pattern (starting with `*`, followed by `!` exceptions). This conflicts with how Tailwind CSS v4 resolves `@source` directives.

Tailwind v4 uses git to determine which files are eligible for scanning. When the `.gitignore` starts with `*`, the entire `vendor/` directory is invisible to git. As a result, any `@source` path pointing into `vendor/` is silently ignored, even when explicitly declared. No warning or error is emitted.

This breaks Hyvä themes, which use `@source` to scan the default theme in `vendor/hyva-themes/magento2-default-theme`:

```css
@import "tailwindcss" source(none);
@source "../../**/*.phtml";
@source "../../**/*.xml";
@source "../../../../../../vendor/hyva-themes/magento2-default-theme";
```

On a project using this repository's `.gitignore`, the last `@source` line produces no output. Styles from the default theme are silently missing from the build.

The standard [Magento 2 `.gitignore`](https://github.com/magento/magento2/blob/2.4-develop/.gitignore) uses a deny-list approach (`/vendor/*` explicitly listed) and does not trigger this issue.

A minimal reproduction is available at: https://github.com/GrimLink/tailwind-gitignore-bug

The underlying Tailwind behavior is tracked at: https://github.com/tailwindlabs/tailwindcss/issues/19844

**Proposed fix:** Align the `.gitignore` in this repository with the deny-list approach used in the Magento 2 core repository, explicitly listing ignored directories rather than denying everything by default.

Start with the repository's .gitignore and compare its allow-list pattern with the Magento 2 deny-list version linked in the issue. Use the linked minimal reproduction or a Tailwind CSS v4 build with the shown @source path, and confirm that files under vendor/ are scanned and their styles are no longer silently omitted.

Written by the indexing model from the issue text.