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-core/src/rules/regex.rs

@@ -0,0 +1,100 @@
+use regex::Regex;
+use serde::{Deserialize, Serialize};
+
+use crate::{NominaError, RenameContext, RenameRule};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RegexRule {
+    pub pattern: String,
+    pub replace_with: String,
+    pub case_insensitive: bool,
+    pub enabled: bool,
+}
+
+impl RegexRule {
+    pub fn new() -> Self {
+        Self {
+            pattern: String::new(),
+            replace_with: String::new(),
+            case_insensitive: false,
+            enabled: true,
+        }
+    }
+
+    fn build_regex(&self) -> std::result::Result<Regex, NominaError> {
+        let pat = if self.case_insensitive {
+            format!("(?i){}", self.pattern)
+        } else {
+            self.pattern.clone()
+        };
+        Regex::new(&pat).map_err(|e| NominaError::InvalidRegex {
+            pattern: self.pattern.clone(),
+            reason: e.to_string(),
+        })
+    }
+}
+
+impl RenameRule for RegexRule {
+    fn apply(&self, filename: &str, _context: &RenameContext) -> String {
+        if self.pattern.is_empty() {
+            return filename.to_string();
+        }
+        match self.build_regex() {
+            Ok(re) => re.replace_all(filename, self.replace_with.as_str()).into_owned(),
+            Err(_) => filename.to_string(),
+        }
+    }
+
+    fn display_name(&self) -> &str {
+        "Regex"
+    }
+
+    fn rule_type(&self) -> &str {
+        "regex"
+    }
+
+    fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn basic_regex() {
+        let rule = RegexRule {
+            pattern: r"(\d+)".into(),
+            replace_with: "NUM".into(),
+            case_insensitive: false,
+            enabled: true,
+        };
+        let ctx = RenameContext::dummy(0);
+        assert_eq!(rule.apply("file123", &ctx), "fileNUM");
+    }
+
+    #[test]
+    fn capture_groups() {
+        let rule = RegexRule {
+            pattern: r"([a-z]+)-([a-z]+)".into(),
+            replace_with: "${2}_${1}".into(),
+            case_insensitive: false,
+            enabled: true,
+        };
+        let ctx = RenameContext::dummy(0);
+        assert_eq!(rule.apply("hello-world", &ctx), "world_hello");
+    }
+
+    #[test]
+    fn empty_pattern() {
+        let rule = RegexRule {
+            pattern: String::new(),
+            replace_with: "x".into(),
+            case_insensitive: false,
+            enabled: true,
+        };
+        let ctx = RenameContext::dummy(0);
+        assert_eq!(rule.apply("test", &ctx), "test");
+    }
+}