initial project scaffold

Rust workspace with nomina-core (rename engine) and nomina-app (Tauri v2 shell).
React/TypeScript frontend with tabbed rule panels, virtual-scrolled file list,
and Zustand state management. All 9 rule types implemented with 25 passing tests.

crates/nomina-app/src/commands/presets.rs

@@ -0,0 +1,72 @@
+use std::path::PathBuf;
+
+use nomina_core::preset::NominaPreset;
+
+#[tauri::command]
+pub async fn save_preset(preset: NominaPreset) -> Result<String, String> {
+    let dir = get_presets_dir();
+    std::fs::create_dir_all(&dir).map_err(|e| e.to_string())?;
+
+    let filename = format!("{}.nomina", sanitize_filename(&preset.name));
+    let path = dir.join(&filename);
+    preset.save(&path).map_err(|e| e.to_string())?;
+
+    Ok(path.to_string_lossy().to_string())
+}
+
+#[tauri::command]
+pub async fn load_preset(path: String) -> Result<NominaPreset, String> {
+    NominaPreset::load(&PathBuf::from(path)).map_err(|e| e.to_string())
+}
+
+#[tauri::command]
+pub async fn list_presets() -> Result<Vec<PresetInfo>, String> {
+    let dir = get_presets_dir();
+    if !dir.exists() {
+        return Ok(Vec::new());
+    }
+
+    let mut presets = Vec::new();
+    let entries = std::fs::read_dir(&dir).map_err(|e| e.to_string())?;
+
+    for entry in entries {
+        let entry = match entry {
+            Ok(e) => e,
+            Err(_) => continue,
+        };
+        let path = entry.path();
+        if path.extension().map(|e| e == "nomina").unwrap_or(false) {
+            if let Ok(preset) = NominaPreset::load(&path) {
+                presets.push(PresetInfo {
+                    name: preset.name,
+                    description: preset.description,
+                    path: path.to_string_lossy().to_string(),
+                });
+            }
+        }
+    }
+
+    Ok(presets)
+}
+
+#[derive(Debug, serde::Serialize)]
+pub struct PresetInfo {
+    pub name: String,
+    pub description: String,
+    pub path: String,
+}
+
+fn get_presets_dir() -> PathBuf {
+    let dirs = directories::ProjectDirs::from("com", "nomina", "Nomina")
+        .expect("failed to get app data directory");
+    dirs.data_dir().join("presets")
+}
+
+fn sanitize_filename(name: &str) -> String {
+    name.chars()
+        .map(|c| match c {
+            '<' | '>' | ':' | '"' | '/' | '\\' | '|' | '?' | '*' => '_',
+            _ => c,
+        })
+        .collect()
+}