chore: update tailwindcss monorepo to v4.1.18

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@tailwindcss/postcss (source)	4.1.17 -> 4.1.18
tailwindcss (source)	4.1.17 -> 4.1.18

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Release Notes

tailwindlabs/tailwindcss (@​tailwindcss/postcss)

v4.1.18

Compare Source

Fixed

• Ensure validation of source(…) happens relative to the file it is in (#​19274)
• Include filename and line numbers in CSS parse errors (#​19282)
• Skip comments in Ruby files when checking for class names (#​19243)
• Skip over arbitrary property utilities with a top-level ! in the value (#​19243)
• Support environment API in @tailwindcss/vite (#​18970)
• Preserve case of theme keys from JS configs and plugins (#​19337)
• Write source maps correctly on the CLI when using --watch (#​19373)
• Handle special defaults (like ringColor.DEFAULT) in JS configs (#​19348)
• Improve backwards compatibility for content theme key from JS configs (#​19381)
• Upgrade: Handle future and experimental config keys (#​19344)
• Try to canonicalize any arbitrary utility to a bare value (#​19379)
• Validate candidates similarly to Oxide (#​19397)
• Canonicalization: combine text-* and leading-* classes (#​19396)
• Correctly handle duplicate CLI arguments (#​19416)
• Don’t emit color-mix fallback rules inside @keyframes (#​19419)
• CLI: Don't hang when output is /dev/stdout (#​19421)

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