Proposal: Allow overwriting static utilities that have a namespace (#18056)

This PR attempts to move static utilities that are overwriteable by a
theme value to be a fallback rather than a conflicting implementation.
The idea is to allow a theme value to take presedence over that static
utility _and cause it not to generate_.

For example, when overwriting the `--radius-full` variant, it should
ensure that the default `rounded-full` no longer emits the
`calc(infinity * 1px)` declaration:

```ts
expect(
  await compileCss(
    css`
      @theme {
        --radius-full: 99999px;
      }
      @tailwind utilities;
    `,
    ['rounded-full'],
  ),
).toMatchInlineSnapshot(`
  ":root, :host {
    --radius-full: 99999px;
  }

  .rounded-full {
    border-radius: var(--radius-full);
  }"
`)
```

This allows anyone who wants `--radius-full` to be a CSS variable to
simply define it in their theme:

```css
@theme {
  /* Make `--radius-full` a CSS variable without the utility generating two CSS classes */
  --radius-full: calc(infinity * 1px);
}
```

The idea is to extend this pattern across all functional utilities that
also have static utilities that can collide with the namespace. This
gives users more control over what they want as CSS variables when the
defaults don't work for them, allowing them to resolve #16639 and #15115
in user space.

You may now find yourself thinking "but Philipp, why would someone want
to be able to overwrite `--animate-none`. `none` surely always will mean
no animation" and I would agree [but it's already possible right now
anyways so this is not a new behavior! This PR just cleans up the
generated output.](https://play.tailwindcss.com/StnQqm4V2e)

---------

Co-authored-by: Robin Malfait <[email protected]>

Author: philipp-spiess

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure that file system watchers created when using the CLI are always cleaned up ([#18905](https://github.com/tailwindlabs/tailwindcss/pull/18905))
 - Do not generate `grid-column` utilities when configuring `grid-column-start` or `grid-column-end` ([#18907](https://github.com/tailwindlabs/tailwindcss/pull/18907))
 - Do not generate `grid-row` utilities when configuring `grid-row-start` or `grid-row-end` ([#18907](https://github.com/tailwindlabs/tailwindcss/pull/18907))
+- Prevent duplicate CSS when overwriting a static utility with a theme key ([#18056](https://github.com/tailwindlabs/tailwindcss/pull/18056))
 
 ## [4.1.13] - 2025-09-03