Tooling: ship VS Code CSS custom-data for `--sf-*` tokens

[jackgranatowski]

Type: author-time tooling · Tier: v1.0

Summary

Generate a css-custom-data.json (VS Code Custom Data format) so --sf-* tokens autocomplete with descriptions in any editor that supports it.

Why

Pure DX win at zero runtime cost — tokens become discoverable in-editor with hover docs. Generated from the same catalogue as the manifest, so it never drifts.

Verified state (2026-06-20)

No css-custom-data.json exists in the repo.

Constraints

Build tooling only. Derive from api-index.json / the published manifest.

Acceptance criteria

• Generate css-custom-data.json from source tokens
• Include description + default value per token
• Regenerate in the docs pipeline
• README snippet for wiring it into .vscode/settings.json