Incorrect CSS minification when using `next build`

### Link to the code that reproduces this issue https://github.com/RobinMalfait/nextjs-incorrect-css-minification ### To Reproduce `next dev` will result in the correct result: <img width="119" alt="Image" src="https://github.com/user-attachments/assets/7a85b2e5-3211-48ce-a8ad-6368cb7f19d6" /> `next build && next start` will result in the incorrect result: <img width="117" alt="Image" src="https://github.com/user-attachments/assets/194cbeb4-4097-45c1-8cc6-5c907010ffaf" /> ### Current vs. Expected behavior Given CSS like this: ```css .example { border: 2px solid red; width: 100px; height: 100px; background-image: conic-gradient(in oklch decreasing hue, oklch(0.491 0.27 292.580994) var(--tw-gradient-from-position), oklch(0.897 0.196 126.665001) 50%, oklch(0.491 0.27 292.580994) 100%); } @property --tw-gradient-from-position { syntax: "<length-percentage>"; inherits: false; initial-value: 0% } ``` This will work as-is in development mode because no minification is happening. Once you run a production build, the `initial-value: 0%` is defined as `initial-value: 0` which makes the CSS property invalid. I expect that the `initial-value` stays the same and not break when running a production build. You also don't get any errors, so it might not be obvious that this bug happened. ### Provide environment information ```bash Operating System: Platform: darwin Arch: arm64 Version: Darwin Kernel Version 24.4.0: Fri Apr 11 18:33:47 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6000 Available memory (MB): 65536 Available CPU cores: 10 Binaries: Node: 23.11.0 npm: 10.9.2 Yarn: N/A pnpm: 9.15.1 Relevant Packages: next: 15.4.0-canary.33 // Latest available version is detected (15.4.0-canary.33). eslint-config-next: N/A react: 19.1.0 react-dom: 19.1.0 typescript: N/A Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) CSS ### Which stage(s) are affected? (Select all that apply) next build (local) ###…