Add bare value support for auto-rows-* and auto-cols-*

[RobinMalfait]

This PR adds bare value support for auto-rows-* and auto-cols-*.

We first introduced auto-rows-auto, auto-rows-min, auto-rows-max and auto-rows-fr (same for auto-cols-*) back in Tailwind CSS v1.9 (https://v1.tailwindcss.com/docs/grid-auto-rows#app) but we haven't touched it since.

This PR now adds support for bare values that use the spacing scale. That means that you can now use auto-rows-12 or auto-cols-12 which will result in the following CSS:

.auto-cols-12 {
  grid-auto-columns: calc(var(--spacing) * 12);
}
.auto-rows-12 {
  grid-auto-rows: calc(var(--spacing) * 12);
}

We could also add support for percentage based values. The only question is what the syntax should be. This can either be auto-rows-3/4 or auto-rows-75%.

For the fraction case, we already have w-3/4 and aspect-3/4 even though they both have a different value as a result:

.aspect-3\/4 {
  aspect-ratio: 3/4;
}
.w-3\/4 {
  width: calc(3 / 4 * 100%);
}

We also have some precedence for the % value as well, e.g. via-10% for gradient color stops.

I think I would personally towards the auto-rows-75% value instead of auto-rows-3/4. The fraction syntax works great for aspect ratio because that's literally what it is (aspect-16/9). The fraction also works great for widths, because you typically have 2 elements next to each other:

<div>
  <div class="w-1/3"></div>
  <div class="w-2/3"></div>
</div>

Since you only use the auto-rows-* once on a parent element, I think the auto-rows-75% makes a bit more sense than auto-rows-3/4 since there is no other element (at least not that I can think of).

TODO

• Support percentages?
  • Syntax A: auto-rows-3/4
  • Syntax B: auto-rows-75%
  • Syntax C: support both, but that seems silly

Percentage support isn't a blocker for this PR, since you can always use auto-rows-[75%] if you want

Test plan

1. Added a test to prove that this works
2. Existing tests still pass

Requested by: #20225

[greptile-apps]

Confidence Score: 5/5

Small, self-contained addition that mirrors an established pattern throughout the file; no existing behavior is changed and new utilities silently no-op when --spacing is absent.

Both handlers follow the exact same guard-then-return pattern as spacingUtility. The --spacing presence check prevents spurious output in themes that omit the variable, and isValidSpacingMultiplier correctly allows decimal multipliers. Tests supply the required theme context and snapshot the expected output. No edge cases are left unhandled.

No files require special attention.

_{Reviews (2): Last reviewed commit: "use `isValidSpacingMultiplier`" | Re-trigger Greptile}

[coderabbitai]

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• packages/tailwindcss/src/utilities.ts

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• packages/tailwindcss/src/utilities.ts

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Walkthrough

This PR introduces support for bare numeric spacing values in auto-cols-* and auto-rows-* utilities. The implementation adds handleBareValue handlers to both utilities in utilities.ts that accept positive integers and emit --spacing(<value>) calculations when theme resolution does not provide a value. Tests are updated to verify the feature works with a custom theme spacing token, and a changelog entry documents the addition.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding bare value support for auto-rows-* and auto-cols-* utilities, which is the core focus of the changeset.
Description check	✅ Passed	The description is directly related to the changeset, providing detailed context about the feature, implementation approach, and test plan for adding bare value support to auto-rows-* and auto-cols-*.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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