substrate pattern attribute: engine enum + shared base gradient stylesheet

Add the substrate pattern attribute with a fixed engine-level enum and a shared, always-included base stylesheet of token-driven gradient recipes.

claude/mcp-server-verify-4lnxej View source

Tracking started Jun 9 — check back for trends.

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claude/mcp-server-verify-4lnxej current ready

Pattern vocabulary is a fixed engine enum (dots|grid|lines|cross|checker|none), not a theme preset registry; none is the empty default.
substrate="dots" plus inline facets substrate-size|opacity|fill work standalone; substrate-fill selects inherit|inset.
Engine emits markers only (data-substrate, --substrate-*); a shared base stylesheet (always included, not per-theme) realises geometry via token-driven gradients, exposing only --substrate-* hooks; patterns track tint/inset colour.
Optional named recipes belong in refrakt.config.json (deferred until inline facets prove insufficient).

Engine emits markers; CSS draws, like data-method. SPEC-087 §1.