feat: export notation as MusicXML

AGENTS.md

@@ -25,6 +25,7 @@ The project is an offline-first MVP. Keep the app local-only: no server, no paid
 - Temporary loop range is separate from saved Regions. Editing a temporary loop must not mutate a saved Region. Editing a saved Region must not silently move the temporary loop unless the user explicitly activates that Region as loop.
 - Waveform, tempo track, region track, notes, loop markers, beat grid, and playhead must share one visible time range. Use `TimelineViewport` for `time <-> pixel`, zoom, pan, bounds, and intersections.
 - The Notation track and Notation window must share score generation, harmony editing actions, selection, and the `AudioPlayerViewModel` playback clock. The window may lay out the full score in multiple systems, but it must not create a second notation storage model or a second playback source of truth.
+- Future Notation features must export through the shared Notation export mechanism so MusicXML and later formats stay in sync with the app's Notation model.
 - Heavy audio work must not run on the main thread. Analysis and peakform generation should stay async/background.
 - Do not use system macOS alert/beep sounds for the metronome. Use the app's metronome sound abstraction.
 - Keep hotkeys centralized in `AppHotkey`; Help > Keyboard Shortcuts is generated from it.

CHANGELOG.md

@@ -8,6 +8,7 @@ development artifact builds use `vMAJOR.MINOR.PATCH-dev.N`.
 
 ## Unreleased
 
+- Added MusicXML export for Notation from the File menu and Notation window.
 - Added a collapsible Notation track in the main timeline, collapsed by default and saved per project.
 - Changed notation harmony entry so beat slashes are selectable and Cmd+K opens chord input for the selected beat.
 - Added notation measure range selection with Shift-click, Cmd+C/Cmd+V measure copy and replace-paste for harmony contents, and Esc to clear the selection.

JammLab.xcodeproj/project.pbxproj

@@ -47,6 +47,8 @@
 		9FCB01062D80000100112233 /* NotationMeasureLayout.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FCB00062D80000100112233 /* NotationMeasureLayout.swift */; };
 		9FEA01052D70000100112233 /* NotationVisibleMeasureFitter.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FEA00052D70000100112233 /* NotationVisibleMeasureFitter.swift */; };
 		9FEA01062D70000100112233 /* ProjectKeySelection.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FEA00062D70000100112233 /* ProjectKeySelection.swift */; };
+		9FEE01012D90000100112233 /* NotationExportService.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FEE00012D90000100112233 /* NotationExportService.swift */; };
+		9FEE01022D90000100112233 /* AudioPlayerViewModel+NotationExport.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FEE00022D90000100112233 /* AudioPlayerViewModel+NotationExport.swift */; };
 		9FCB01072D80000100112233 /* NotationHarmonyInlineTextField.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FCB00072D80000100112233 /* NotationHarmonyInlineTextField.swift */; };
 		9FEC01012D71000100112233 /* NotationWindowView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9FEC00012D71000100112233 /* NotationWindowView.swift */; };
 		9F8B01062C10000100112233 /* TestSupport.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9F8B00072C10000100112233 /* TestSupport.swift */; };
@@ -212,6 +214,8 @@
 		9FCB00062D80000100112233 /* NotationMeasureLayout.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotationMeasureLayout.swift; sourceTree = "<group>"; };
 		9FEA00052D70000100112233 /* NotationVisibleMeasureFitter.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotationVisibleMeasureFitter.swift; sourceTree = "<group>"; };
 		9FEA00062D70000100112233 /* ProjectKeySelection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProjectKeySelection.swift; sourceTree = "<group>"; };
+		9FEE00012D90000100112233 /* NotationExportService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotationExportService.swift; sourceTree = "<group>"; };
+		9FEE00022D90000100112233 /* AudioPlayerViewModel+NotationExport.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "AudioPlayerViewModel+NotationExport.swift"; sourceTree = "<group>"; };
 		9FCB00072D80000100112233 /* NotationHarmonyInlineTextField.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotationHarmonyInlineTextField.swift; sourceTree = "<group>"; };
 		9FEC00012D71000100112233 /* NotationWindowView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotationWindowView.swift; sourceTree = "<group>"; };
 		9F8B00062C10000100112233 /* JammLabTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = JammLabTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -394,6 +398,7 @@
 				9F8A00172C00000100112233 /* BeatGridCalculator.swift */,
 				9F8A00182C00000100112233 /* MetronomeClickScheduler.swift */,
 				9FCB00062D80000100112233 /* NotationMeasureLayout.swift */,
+				9FEE00012D90000100112233 /* NotationExportService.swift */,
 				9FEA00032D70000100112233 /* NotationViewportFactory.swift */,
 				9FEA00052D70000100112233 /* NotationVisibleMeasureFitter.swift */,
 				9F8A00192C00000100112233 /* ProjectArtifactStore.swift */,
@@ -427,6 +432,7 @@
 				9FB201032D30000100112233 /* AudioPlayerViewModel+Stems.swift */,
 				9FB201042D30000100112233 /* AudioPlayerViewModel+Timeline.swift */,
 				9FB201052D30000100112233 /* AudioPlayerViewModel+Notes.swift */,
+				9FEE00022D90000100112233 /* AudioPlayerViewModel+NotationExport.swift */,
 				9FB201062D30000100112233 /* AudioPlayerViewModel+Video.swift */,
 				9FB201072D30000100112233 /* AudioPlayerViewModel+UndoDirty.swift */,
 			);
@@ -753,6 +759,7 @@
 				9FB200032D30000100112233 /* AudioPlayerViewModel+Stems.swift in Sources */,
 				9FB200042D30000100112233 /* AudioPlayerViewModel+Timeline.swift in Sources */,
 				9FB200052D30000100112233 /* AudioPlayerViewModel+Notes.swift in Sources */,
+				9FEE01022D90000100112233 /* AudioPlayerViewModel+NotationExport.swift in Sources */,
 				9FB200062D30000100112233 /* AudioPlayerViewModel+Video.swift in Sources */,
 				9FB200072D30000100112233 /* AudioPlayerViewModel+UndoDirty.swift in Sources */,
 				9F8C01032C20000100112233 /* AppControls.swift in Sources */,
@@ -787,6 +794,7 @@
 				9FEC01012D71000100112233 /* NotationWindowView.swift in Sources */,
 				9F8A010D2C00000100112233 /* AppHotkey.swift in Sources */,
 				9FCB01062D80000100112233 /* NotationMeasureLayout.swift in Sources */,
+				9FEE01012D90000100112233 /* NotationExportService.swift in Sources */,
 				9FEA01032D70000100112233 /* NotationViewportFactory.swift in Sources */,
 				9FEA01052D70000100112233 /* NotationVisibleMeasureFitter.swift in Sources */,
 				9FEA01022D70000100112233 /* NotationViewportState.swift in Sources */,

JammLab/JammLabApp.swift

@@ -124,6 +124,15 @@ struct JammLabCommands: Commands {
                 }
             }
             .keyboardShortcut("s", modifiers: [.command, .shift])
+
+            Divider()
+
+            Button("Export Notation as MusicXML...") {
+                Task {
+                    await viewModel.exportNotationAsMusicXML()
+                }
+            }
+            .disabled(!viewModel.canExportNotation)
         }
 
         CommandGroup(replacing: .undoRedo) {