refactor(www): upgrade tailwind-variants, drop tailwind-merge and cnfast

[mehdibha]

Summary

Upgrades tailwind-variants to 3.3.0 — the full TypeScript rewrite (heroui-inc/tailwind-variants#301) that vendors the tailwind-merge engine — and consolidates the design system's styling dependencies onto that single package:

• tailwind-merge removed (www dep + shipped registry deps). It was only ever listed as tv's optional peer; 3.3.0 never imports it at runtime.
• cnfast removed. cn in registry/lib/utils now wraps tv's own cn, narrowed to string (React Aria className render props reject undefined). The publisher's init-emitted src/lib/utils.ts ships the same wrapper (CN_UTILS_TS, now exported and reused by the publish smoke test's fixture).
• InferTv adapted in lib/styles.tsx: TVReturnType is now an interface with a 6th E (extend) type param; composed tv objects carry a real extend, so the cast passes TVReturnTypeLike<never, never> | undefined.

Users installing components now get tailwind-variants instead of tailwind-variants + tailwind-merge + cnfast.

Why 3.3.0 is safe (verified)

• Merge parity: A/B harness ran identical configs through 3.2.2 + tailwind-merge 3.4.0 vs 3.3.0's built-in engine — extend chains (the exact shape createStyles composes for density/params), slots, className overrides, v4 syntax (rounded-(--btn-radius), **:[svg]:) — byte-identical output on every case.
• cn parity: tv's cn vs cnfast — identical on strings, objects, nested arrays, falsy values, and merge conflicts.
• Perf: invoking a composed tv function dropped 1.15µs → 0.25µs (~4.6×), extend-chain creation 1.70µs → 1.29µs. This is per-render work across every registry component.
• Upstream fixes we inherit: variant types lost on extend (feat(create): algorithm picker (oklch / tailwind / material / contrast) #185), compoundSlots+extend (feat: enhance landing page #199), compoundVariants+slots+defaultVariants (refactor(www): decouple accordion from disclosure parts #238), falsy boolean compound variants (refactor(www): reorganize docs + revamp the components gallery (/docs/components) #209). The one behavioral break (empty slots: {} enables slot mode) has zero occurrences here.
• pnpm build:registry (zero drift in tracked generated output), typecheck, test (235), check all green; the publish smoke test type-checks the full emitted set against the new utils.

Notes

• Merging is now unconditional — on 3.2.2 it silently turned off if tailwind-merge wasn't installed next to tv.
• Trade-off: the vendored engine snapshots tailwind-merge's class tables, so recognition of future Tailwind utilities now tracks tv releases. Unknown classes are left untouched, so our custom utilities (focus-ring, cursor-interactive, …) are unaffected. Consumers who use tailwind-merge for their own code will carry both engines (~7KB gzip overlap) — their call.
• compoundVariants/compoundSlots are now reliable with the runtime extend chains — previously unused in the registry (0/49 styles.ts); style authors can reach for them.

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Project	Deployment	Actions	Updated (UTC)
dotui	Ready	Preview	Jul 31, 2026 10:04pm