Initial commit: MTG personal library catalog (Tauri v2 + React/TS)

Full working app with:
- Rust core (mtgc-core): Scryfall ingester, nucleo fuzzy search, SQLite two-DB
  architecture (reference.db + library.db via ATTACH), criteria filters, deck ops
- Tauri v2 shell exposing the core as typed IPC commands
- React/TS frontend: card entry, library browser, deck editor
- Features: fuzzy card search, color/CMC/type/commander-identity filters,
  tile/list view toggle, hover card previews, deck format + commander support,
  per-card location field, grouping by type/subtype/CMC/color, localStorage
  persistence for active tab/deck/grouping, Discord-inspired dark UI (#C8553D accent)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src-tauri/src/state.rs

@@ -0,0 +1,58 @@
+//! App state: the open [`Catalog`] and fuzzy [`NameIndex`], plus the db paths.
+
+use std::path::PathBuf;
+
+use mtgc_core::{Catalog, NameIndex};
+
+/// Managed application state, guarded by a `Mutex` in Tauri's state store.
+pub struct AppState {
+    pub library_path: PathBuf,
+    pub reference_path: PathBuf,
+    pub catalog: Option<Catalog>,
+    pub index: Option<NameIndex>,
+}
+
+impl AppState {
+    /// Initialize with default paths under the app data dir and open the catalog
+    /// if a reference db already exists.
+    pub fn new(data_dir: PathBuf) -> Self {
+        let mut s = Self {
+            library_path: data_dir.join("library.db"),
+            reference_path: data_dir.join("reference.db"),
+            catalog: None,
+            index: None,
+        };
+        // Best-effort open; failures just leave the catalog unloaded.
+        let _ = s.reopen();
+        s
+    }
+
+    /// (Re)open the catalog + rebuild the name index. Only opens when a reference
+    /// db exists — attaching a non-existent file would create an empty (tableless)
+    /// db and make every query fail.
+    pub fn reopen(&mut self) -> Result<(), String> {
+        if self.reference_path.exists() {
+            let catalog = Catalog::open(&self.library_path, &self.reference_path)
+                .map_err(|e| e.to_string())?;
+            let index = catalog.build_name_index().map_err(|e| e.to_string())?;
+            self.index = Some(index);
+            self.catalog = Some(catalog);
+        } else {
+            self.catalog = None;
+            self.index = None;
+        }
+        Ok(())
+    }
+
+    pub fn catalog(&self) -> Result<&Catalog, String> {
+        self.catalog
+            .as_ref()
+            .ok_or_else(|| "Card data not loaded yet — click 'Download card data'.".to_string())
+    }
+
+    pub fn index(&self) -> Result<&NameIndex, String> {
+        self.index
+            .as_ref()
+            .ok_or_else(|| "Card data not loaded yet — click 'Download card data'.".to_string())
+    }
+}