Tokens: register `@property` for shadow, radius, and space output tokens

[jackgranatowski]

Type: additive CSS · Tier: v1.0

Summary

Extend typed @property registration beyond colors and the fluid scalars to the shadow, radius, and spacing output tokens, so layout values become animatable and inspect cleanly in DevTools.

Why

Enables transitions on spacing/shadow/radius and gives correct typed values in DevTools — a concrete DX + capability gain at no runtime cost.

Verified state (2026-06-20)

@property is currently registered for colors (33) and fluid scalars (6 + 4 space scalars: --sf-space-ratio/base-min/max) only. Confirmed @property --sf-shadow* = 0, @property --sf-radius* = 0, and the space output tokens (--sf-space-m, etc.) are not registered.

Constraints

Additive, no build, no JS. Must keep inherits/initial-value correct so unsupporting engines fall back to initial gracefully.

Acceptance criteria

• @property for --sf-shadow-*, --sf-radius-*, and --sf-space-* output tokens
• Verify no regression in computed values (token regression suite)
• Docs note on which tokens are now animatable