Frontend polish: smooth motion, live perf, clean UX

Phase 1 (motion): animate Focus-mode layout swap, ParamPanel tab switch
with underline slide, sidebar/setlist diffable inserts, AevumToggle
spring, sheet/overlay transitions, FirstRun→ContentView cross-fade.

Phase 2 (performance): KnobFloat polling 10Hz→4Hz + pauses when
backgrounded; LiveWaveformView pauses 60fps redraw when stopped and
pre-samples gradient colors; SetlistView computes similarity off
@mainactor with a spinner; new loopsBySong + loopToSlot indexes kill
O(N×M) per-render filters and O(6) per-cell scans; MetricsView +
Performance tab self-throttle at 4Hz; forever-animations pause when
scenePhase != .active; setBlendWeights batches Normalize into one
publish; slot(forLoop:) is O(1).

Phase 3 (clean): GlassBackground uses .ultraThinMaterial; new AevumFont
hero/section tokens replace raw .system calls; WaveformView no longer
invisible in light mode and playhead matches the palette; capsuleChip
modifier unifies badge styling; sidebar rows get .contentShape;
MacroKnobs get tooltips; DRUMS becomes a proper detented 2-position knob.

Phase 4 (live): space/R shortcuts are now ⌘Space/⌘R so they don't fire
inside text fields; ⇧⌘R records (closes the long-standing ⌘R-disabled
gap); menu commands call controller directly instead of round-tripping
through NotificationCenter; arrow-key cursor nudge is smaller and
spring-animated; trackpad haptic on scene recall and slot toggle;
RelativeDateTimeFormatter + ByteCountFormatter cached; NamePromptSheet
inits @State in init (no empty-field flash) and wires Enter/Escape.

Plan: docs/FRONTEND_PLAN.md

Author: Stella

Aevum/Sources/AevumApp/AevumApp.swift

@@ -28,32 +28,54 @@ struct AevumApp: App {
 
     var body: some SwiftUI.Scene {
         WindowGroup {
-            if modelsReady {
-                ContentView()
-                    .environmentObject(controller)
-                    .frame(minWidth: 1200, minHeight: 750)
-                    .task { if !controller.isEngineLoaded { await controller.loadEngine() } }
-            } else {
-                FirstRunView { modelsReady = true }
+            Group {
+                if modelsReady {
+                    ContentView()
+                        .environmentObject(controller)
+                        .frame(minWidth: 1200, minHeight: 750)
+                        .task { if !controller.isEngineLoaded { await controller.loadEngine() } }
+                } else {
+                    FirstRunView { withAnimation(.easeInOut(duration: 0.35)) { modelsReady = true } }
+                }
             }
+            .animation(.easeInOut(duration: 0.35), value: modelsReady)
+            .transition(.opacity)
         }
         .windowStyle(.titleBar)
         .commands {
             CommandGroup(after: .newItem) {
+                Button("New Project…") {
+                    NotificationCenter.default.post(name: .newProject, object: nil)
+                }.keyboardShortcut("n", modifiers: [.command, .shift])
+
+                Button("Save Project") {
+                    controller.saveCurrentProject()
+                }.keyboardShortcut("s", modifiers: [.command])
+
+                Button("Duplicate Project") {
+                    if let current = controller.currentProject {
+                        controller.duplicateProject(current)
+                    }
+                }.keyboardShortcut("s", modifiers: [.command, .shift])
+
                 Button("Import Songs…") {
                     NotificationCenter.default.post(name: .importSongs, object: nil)
                 }.keyboardShortcut("i", modifiers: [.command])
 
                 Button("Play / Stop") {
-                    NotificationCenter.default.post(name: .togglePlay, object: nil)
-                }.keyboardShortcut(" ", modifiers: [])
+                    controller.togglePlay()
+                }.keyboardShortcut(" ", modifiers: [.command])
 
                 Button("Reset Engine") {
-                    NotificationCenter.default.post(name: .triggerReset, object: nil)
-                }.keyboardShortcut("r", modifiers: [])
+                    controller.triggerReset()
+                }.keyboardShortcut("r", modifiers: [.command])
+
+                Button("Record Live Output") {
+                    controller.toggleRecording()
+                }.keyboardShortcut("r", modifiers: [.command, .shift])
 
                 Button("Focus Mode") {
-                    NotificationCenter.default.post(name: .toggleFocused, object: nil)
+                    controller.toggleFocused()
                 }.keyboardShortcut("f", modifiers: [.command])
             }
         }
@@ -62,7 +84,5 @@ struct AevumApp: App {
 
 extension Notification.Name {
     static let importSongs = Notification.Name("Aevum.importSongs")
-    static let togglePlay = Notification.Name("Aevum.togglePlay")
-    static let triggerReset = Notification.Name("Aevum.triggerReset")
-    static let toggleFocused = Notification.Name("Aevum.toggleFocused")
+    static let newProject = Notification.Name("Aevum.newProject")
 }