Per-app Tailwind compilation for optimized renderer bundles

[jlowin]

Context

With #362, the renderer now uses @tailwindcss/browser for runtime CSS generation — any Tailwind class works in css_class without a safelist. This is the right default for most users.

For advanced use cases (smaller bundles, offline support, faster first paint), a per-app compilation step could produce a renderer with only the CSS the app actually needs, without the ~60KB runtime compiler overhead.

Design

The idea: pass all possible views to a compiler that extracts the Tailwind classes used and runs Tailwind to generate exact CSS.

app = PrefabApp(
    view=my_view,
    extra_classes=collect_css_classes(dynamic_card_a, dynamic_card_b),
)
compiled_html = app.compile()  # runs Tailwind, produces optimized HTML

Key decisions:

• Requires Node — Tailwind is the CSS engine, no reimplementation
• Input: serialized view trees + extra_classes for dynamic content (slots, LLM-generated views)
• Output: self-contained HTML with minimal CSS
• collect_css_classes() utility extracts classes from components for the extra_classes param

Prior discussion

Designed in the #352 conversation. The "light" approach (runtime browser compiler) shipped in v0.15.0. This is the "heavy" approach for users who want optimized builds.