chore: add changeset for uncompiled CSS architecture

Author: yahyafakhroji

.changeset/uncompiled-css-architecture.md

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+---
+"@datum-cloud/datum-ui": minor
+---
+
+Ship uncompiled CSS instead of compiled Tailwind output (fixes #16)
+
+- **Breaking:** Grid and NProgress CSS are now separate optional imports (`@datum-cloud/datum-ui/grid`, `@datum-cloud/datum-ui/nprogress`)
+- **Breaking:** Requires Tailwind CSS v4.0.7+ (v4.2.1+ recommended)
+- Removed CSS compilation from build pipeline — raw CSS files are copied to dist
+- Embedded `@source` directive in shipped CSS for zero-config consumer class scanning
+- Pre-expanded grid system `@apply` directives into self-contained CSS
+- Eliminated duplicate Tailwind stylesheets that caused responsive utility conflicts