Implement optional discussion mode

Tests/MusicAssistantCoreTests/AIServiceTests.swift

@@ -24,6 +24,24 @@ final class AIServiceTests: XCTestCase {
         XCTAssertEqual(result.followUpQuestions, ["Should the chorus be bigger?"])
     }
 
+    func testProviderIndependentServiceReturnsDiscussionQuestionsWithoutProjectUpdate() async throws {
+        let service = MockAIService()
+        let project = SongProject(
+            title: "Discussion Project",
+            idea: "Plan the chorus",
+            conversationMode: .discuss
+        )
+        let request = SongProjectDiscussionRequest(
+            context: AIRequestContext(userInstruction: "Ask what is still missing."),
+            project: project
+        )
+
+        let result = try await service.discussSongProject(from: request)
+
+        XCTAssertEqual(result.questions, ["Which vocal delivery should lead the chorus?"])
+        XCTAssertEqual(result.notes, ["Discussion only; no project update was proposed."])
+    }
+
     func testProviderIndependentServiceRevisesLyricsWithStructuredResult() async throws {
         let service = MockAIService()
         let project = SongProject(title: "Lyric Project", idea: "Improve words")
@@ -71,6 +89,13 @@ private struct MockAIService: AIService {
         )
     }
 
+    func discussSongProject(from request: SongProjectDiscussionRequest) async throws -> SongProjectDiscussionResult {
+        SongProjectDiscussionResult(
+            questions: ["Which vocal delivery should lead the chorus?"],
+            notes: ["Discussion only; no project update was proposed."]
+        )
+    }
+
     func reviseLyrics(from request: LyricsRevisionRequest) async throws -> LyricsRevisionResult {
         LyricsRevisionResult(
             lyrics: Lyrics(text: "\(request.sourceLyrics.text)\n\(request.context.userInstruction)"),