Honor explicit search prefixes in SourceFinder

Updated `SourceFinder` to respect explicit `ytsearch:`, `ytmsearch:`, and `scsearch:` prefixes regardless of the configured search engine. Added unit tests to ensure correct behavior and consistent identifier resolution when explicit prefixes are provided.

src/main/java/me/bobert/netneutrality/music/SourceFinder.java

@@ -77,6 +77,18 @@ public class SourceFinder {
             return AudioSourceType.DirectLinkMp3;
         }
 
+        if (url.startsWith("ytsearch:")) {
+            return AudioSourceType.YTSearch;
+        }
+
+        if (url.startsWith("ytmsearch:")) {
+            return AudioSourceType.YTMSearch;
+        }
+
+        if (url.startsWith("scsearch:")) {
+            return AudioSourceType.SCSearch;
+        }
+
         if (!(url.startsWith("http://") || url.startsWith("https://"))) {
             return switch (searchEngine) {
                 case YTMUSIC -> AudioSourceType.YTMSearch;
@@ -102,9 +114,9 @@ public class SourceFinder {
 
         identifier = switch (getSource(url, searchEngine)) {
             case Youtube, YTMusic, Soundcloud, DirectLinkMp3 -> url;
-            case YTSearch -> "ytsearch:" + url;
-            case YTMSearch -> "ytmsearch:" + url;
-            case SCSearch -> "scsearch:" + url;
+            case YTSearch -> url.startsWith("ytsearch:") ? url : "ytsearch:" + url;
+            case YTMSearch -> url.startsWith("ytmsearch:") ? url : "ytmsearch:" + url;
+            case SCSearch -> url.startsWith("scsearch:") ? url : "scsearch:" + url;
             // Udio is not resolvable by the Lavalink node until the source is ported to a
             // server-side plugin, see docs/reference/udio-lavalink-plugin.
             default -> null;

src/test/java/me/bobert/netneutrality/music/SourceFinderTest.java

@@ -48,4 +48,25 @@ public class SourceFinderTest {
         assertEquals(SourceFinder.AudioSourceType.Soundcloud, SourceFinder.getSource(url, SourceFinder.SearchEngine.YTMUSIC));
         assertEquals(url, SourceFinder.getIdentifier(url, SourceFinder.SearchEngine.YTMUSIC));
     }
+
+    @Test
+    public void explicitScsearchPrefixIsHonoredRegardlessOfSearchEngine() {
+        String query = "scsearch:never gonna give you up";
+        assertEquals(SourceFinder.AudioSourceType.SCSearch, SourceFinder.getSource(query, SourceFinder.SearchEngine.YOUTUBE));
+        assertEquals(query, SourceFinder.getIdentifier(query, SourceFinder.SearchEngine.YOUTUBE));
+    }
+
+    @Test
+    public void explicitYtsearchPrefixIsHonoredRegardlessOfSearchEngine() {
+        String query = "ytsearch:never gonna give you up";
+        assertEquals(SourceFinder.AudioSourceType.YTSearch, SourceFinder.getSource(query, SourceFinder.SearchEngine.SOUNDCLOUD));
+        assertEquals(query, SourceFinder.getIdentifier(query, SourceFinder.SearchEngine.SOUNDCLOUD));
+    }
+
+    @Test
+    public void explicitYtmsearchPrefixIsHonoredRegardlessOfSearchEngine() {
+        String query = "ytmsearch:never gonna give you up";
+        assertEquals(SourceFinder.AudioSourceType.YTMSearch, SourceFinder.getSource(query, SourceFinder.SearchEngine.SOUNDCLOUD));
+        assertEquals(query, SourceFinder.getIdentifier(query, SourceFinder.SearchEngine.SOUNDCLOUD));
+    }
 }