fix: cn keeps text-title and text-body next to a text color

[zyx1121]

Stock tailwind-merge rules read our custom text-title / text-body as text colors, so cn("text-body", "text-foreground") returned text-foreground and the size was silently dropped in every component that also sets a text color (button, badge, dialog description…). It went unnoticed because the inherited size is also 16px; it showed in #56, where a 24px label rendered at 16px.

• registry/winlab/lib/utils.ts (the utils item, installed at @/lib/utils) now builds cn with createCn from cn/config, registering title and body as font sizes.
• All 25 components and blocks import cn from it and list utils as a registry dependency.
• CI: the check job asserts cn("text-body text-title", "text-foreground") === "text-title text-foreground"; smoke checks the installed lib/utils.ts and button import.

Verified on sandbox: all checks and build pass; cn("text-body", "text-muted-foreground") now keeps both, cn("bg-primary", "bg-muted") still merges to bg-muted.

🤖 Generated with Claude Code