test: verify startsWith LIKE metachar escaping; document non-atomic edit writes

Music/ContentView.swift

@@ -354,6 +354,9 @@ struct ContentView: View {
             SmartPlaylistBuilderSheet(
                 editingPlaylist: smart,
                 onSave: { name, conditions in
+                    // Two separate writes: consistent with how mutations are handled throughout the UI.
+                    // Partial failure (rename succeeds, conditions fail) is accepted given error
+                    // feedback is not implemented at the UI layer.
                     if name != smart.name {
                         try? playlist.renameSmartPlaylist(smart, to: name)
                     }

MusicTests/SmartPlaylistTests.swift

@@ -267,6 +267,24 @@ struct SmartPlaylistTests {
         #expect((results[0].year ?? 0) < 2000)
     }
 
+    // Verifies that the startsWith operator treats % and _ as literal characters,
+    // not LIKE wildcards — confirming the ESCAPE clause in buildWhereClause works.
+    @Test func startsWithEscapesLIKEMetachars() throws {
+        // Step 1: Insert a track whose artist literally contains "%" and one whose
+        //         artist matches the % wildcard pattern but not the literal prefix
+        // Step 2: Search with startsWith "A%B" — only the literal match should return
+        // Step 3: Verify only the literal "A%B Band" track is returned, not "AXB Band"
+        let db = try DatabaseService(inMemory: true)
+        var t1 = Track.fixture(fileURL: "/a.mp3", artist: "A%B Band")
+        var t2 = Track.fixture(fileURL: "/b.mp3", artist: "AXB Band")
+        try db.insert(&t1)
+        try db.insert(&t2)
+        let conditions = [SmartPlaylistCondition(field: .artist, op: .startsWith, value: .string("A%B"))]
+        let results = try db.fetchTracks(conditions: conditions, sortColumn: "title", ascending: true)
+        #expect(results.count == 1)
+        #expect(results[0].artist == "A%B Band")
+    }
+
     // Updates the conditions of a structured smart playlist and verifies the updated
     // conditions are persisted and fetch back correctly.
     @Test func updateSmartPlaylistConditionsPersists() throws {