feat(ai): bundle four built-in design-system variable presets

Complete shadcn-vocabulary token tables (background/card/primary/muted/
sidebar families plus font and radius tokens) with Light+Dark theme
values, parsed once from a bundled asset and exposed with a
set_variables-ready payload per preset. Groundwork for the
apply-design-system tool and shadcn-aligned variable naming.

crates/op-ai-skills/Cargo.toml

@@ -7,6 +7,7 @@ license.workspace = true
 description = "OpenPencil AI skill engine — phase-driven prompt-skill resolution, ported from the TS pen-ai-skills package"
 
 [dependencies]
+serde_json = { workspace = true }
 # Embeds the skill / style-guide markdown corpus into the crate at
 # compile time so the engine ships self-contained — no runtime file
 # IO, and the crate stays usable on wasm32 targets. Pure Rust.

crates/op-ai-skills/src/design_systems.rs

@@ -0,0 +1,89 @@
+//! Built-in design systems — complete shadcn-vocabulary variable presets
+//! (`--background` / `--card` / `--primary` / `--muted` / the `--sidebar-*`
+//! family, plus font and radius tokens), each with Light + Dark theme
+//! values. Applying one gives a generated design a real token system to
+//! reference (`$--primary`) and free light/dark theming, and aligns our
+//! variable naming with the shadcn convention the wider ecosystem shares.
+
+use std::sync::OnceLock;
+
+const PRESETS_JSON: &str = include_str!("../skills/design-systems.json");
+
+/// One built-in design system: its id and the raw `variables` object in the
+/// exact TS shape `set_variables` accepts.
+#[derive(Debug, Clone)]
+pub struct DesignSystemPreset {
+    pub name: &'static str,
+    /// JSON object string: `name -> { type, value }` definitions.
+    pub variables_json: String,
+    pub variable_count: usize,
+}
+
+fn presets() -> &'static Vec<DesignSystemPreset> {
+    static CACHE: OnceLock<Vec<DesignSystemPreset>> = OnceLock::new();
+    CACHE.get_or_init(|| {
+        let root: serde_json::Value =
+            serde_json::from_str(PRESETS_JSON).expect("bundled design-systems.json parses");
+        let mut out = Vec::new();
+        for name in ["halo", "lunaris", "nitro", "shadcn"] {
+            let Some(vars) = root.get(name).and_then(|ds| ds.get("variables")) else {
+                continue;
+            };
+            out.push(DesignSystemPreset {
+                name: match name {
+                    "halo" => "halo",
+                    "lunaris" => "lunaris",
+                    "nitro" => "nitro",
+                    _ => "shadcn",
+                },
+                variables_json: vars.to_string(),
+                variable_count: vars.as_object().map(|o| o.len()).unwrap_or(0),
+            });
+        }
+        out
+    })
+}
+
+/// All built-in design systems.
+pub fn design_system_presets() -> &'static [DesignSystemPreset] {
+    presets()
+}
+
+/// Look up one preset by (case-insensitive) name.
+pub fn design_system_preset(name: &str) -> Option<&'static DesignSystemPreset> {
+    let lowered = name.trim().to_ascii_lowercase();
+    presets().iter().find(|preset| preset.name == lowered)
+}
+
+/// The theme axis every preset shares.
+pub fn design_system_themes_json() -> &'static str {
+    r#"{"Mode":["Light","Dark"]}"#
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn all_four_presets_load_with_shadcn_core_tokens() {
+        let presets = design_system_presets();
+        assert_eq!(presets.len(), 4);
+        for preset in presets {
+            assert!(preset.variable_count >= 28, "{}", preset.name);
+            for token in [
+                "--background",
+                "--primary",
+                "--muted-foreground",
+                "--sidebar",
+            ] {
+                assert!(
+                    preset.variables_json.contains(token),
+                    "{} missing {token}",
+                    preset.name
+                );
+            }
+        }
+        assert!(design_system_preset("HALO").is_some());
+        assert!(design_system_preset("nope").is_none());
+    }
+}

crates/op-ai-skills/src/lib.rs

@@ -21,6 +21,7 @@ use include_dir::{include_dir, Dir};
 pub mod budget;
 pub mod color;
 pub mod compose;
+pub mod design_systems;
 pub mod frontmatter;
 pub mod loader;
 pub mod memory;