Add library_stats aggregate query for the sidebar summary

New LibraryStats (unique cards owned, total copies, deck count, and
per-color copy counts including colorless) via Catalog::library_stats,
tested against the fixture catalog.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

crates/mtgc-core/src/library.rs

@@ -6,7 +6,7 @@ use rusqlite::{params, OptionalExtension};
 
 use crate::db::REF_DB;
 use crate::error::Result;
-use crate::model::{CardRef, ColorSet, LibraryCard};
+use crate::model::{CardRef, ColorSet, LibraryCard, LibraryStats, WUBRG};
 use crate::Catalog;
 
 /// Map a row shaped `(oracle_id, quantity_owned, location, name, mana_value,
@@ -94,6 +94,56 @@ impl Catalog {
             .collect())
     }
 
+    /// Aggregate stats about the owned library, for the sidebar summary.
+    pub fn library_stats(&self) -> Result<LibraryStats> {
+        let unique_cards: i64 = self.conn.query_row(
+            "SELECT COUNT(*) FROM library_cards WHERE quantity_owned > 0",
+            [],
+            |r| r.get(0),
+        )?;
+        let total_copies: i64 = self.conn.query_row(
+            "SELECT COALESCE(SUM(quantity_owned), 0) FROM library_cards",
+            [],
+            |r| r.get(0),
+        )?;
+        let deck_count: i64 = self
+            .conn
+            .query_row("SELECT COUNT(*) FROM decks", [], |r| r.get(0))?;
+
+        let mut color_counts = [0i64; 5];
+        let mut colorless_count = 0i64;
+        {
+            let mut stmt = self.conn.prepare(&format!(
+                "SELECT oc.colors, lc.quantity_owned
+                 FROM library_cards lc
+                 JOIN {REF_DB}.oracle_cards oc ON oc.oracle_id = lc.oracle_id
+                 WHERE lc.quantity_owned > 0"
+            ))?;
+            let rows =
+                stmt.query_map([], |r| Ok((r.get::<_, i64>(0)? as u8, r.get::<_, i64>(1)?)))?;
+            for row in rows {
+                let (colors, qty) = row?;
+                if colors == 0 {
+                    colorless_count += qty;
+                } else {
+                    for (i, (bit, _)) in WUBRG.iter().enumerate() {
+                        if colors & bit != 0 {
+                            color_counts[i] += qty;
+                        }
+                    }
+                }
+            }
+        }
+
+        Ok(LibraryStats {
+            unique_cards,
+            total_copies,
+            deck_count,
+            color_counts,
+            colorless_count,
+        })
+    }
+
     /// Set the free-text storage location for a card (creates the library row if
     /// absent). Empty string clears it.
     pub fn set_location(&self, oracle_id: &str, location: &str) -> Result<()> {
@@ -157,6 +207,25 @@ mod tests {
         assert_eq!(sol.card.image_uri, "http://img/sol-ring");
     }
 
+    #[test]
+    fn library_stats_aggregates_counts_and_colors() {
+        let fx = test_support::make();
+        let cat = &fx.catalog;
+        cat.add_owned("llanowar-elves", 2).unwrap(); // G
+        cat.add_owned("deathrite-shaman", 1).unwrap(); // BG
+        cat.add_owned("sol-ring", 3).unwrap(); // colorless
+        cat.create_deck("Deck A", None).unwrap();
+        cat.create_deck("Deck B", None).unwrap();
+
+        let stats = cat.library_stats().unwrap();
+        assert_eq!(stats.unique_cards, 3);
+        assert_eq!(stats.total_copies, 6);
+        assert_eq!(stats.deck_count, 2);
+        assert_eq!(stats.colorless_count, 3);
+        // WUBRG order: W, U, B, R, G.
+        assert_eq!(stats.color_counts, [0, 0, 1, 0, 3]);
+    }
+
     #[test]
     fn back_image_uri_is_plumbed_through() {
         let fx = test_support::make();