Initial commit: HUDini — classic volume HUD for macOS

Menu bar utility that shows a centered HUD overlay with volume bars
when system volume changes. CoreAudio monitoring, auto-fade, works
on all spaces and fullscreen.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Sources/HUDini/HUDPanel.swift

@@ -0,0 +1,68 @@
+import Cocoa
+import SwiftUI
+
+class HUDPanel {
+    private var panel: NSPanel?
+    private var hideTimer: Timer?
+    private let hudSize = NSSize(width: 200, height: 200)
+
+    func show(volume: Float, isMuted: Bool) {
+        hideTimer?.invalidate()
+
+        if panel == nil {
+            createPanel()
+        }
+
+        guard let panel = panel else { return }
+
+        // Update content
+        let hostingView = NSHostingView(rootView: HUDView(volume: volume, isMuted: isMuted))
+        hostingView.frame = NSRect(origin: .zero, size: hudSize)
+        panel.contentView = hostingView
+
+        // Center on main screen
+        if let screen = NSScreen.main {
+            let screenFrame = screen.visibleFrame
+            let x = screenFrame.midX - hudSize.width / 2
+            let y = screenFrame.midY - hudSize.height / 2
+            panel.setFrameOrigin(NSPoint(x: x, y: y))
+        }
+
+        // Show
+        panel.alphaValue = 1.0
+        panel.orderFrontRegardless()
+
+        // Auto-hide after 1.5s
+        hideTimer = Timer.scheduledTimer(withTimeInterval: 1.5, repeats: false) { [weak self] _ in
+            self?.fadeOut()
+        }
+    }
+
+    private func createPanel() {
+        let panel = NSPanel(
+            contentRect: NSRect(origin: .zero, size: hudSize),
+            styleMask: [.borderless, .nonactivatingPanel],
+            backing: .buffered,
+            defer: false
+        )
+        panel.level = .floating
+        panel.isOpaque = false
+        panel.backgroundColor = .clear
+        panel.hasShadow = true
+        panel.hidesOnDeactivate = false
+        panel.collectionBehavior = [.canJoinAllSpaces, .fullScreenAuxiliary, .ignoresCycle]
+        panel.isMovableByWindowBackground = false
+        panel.ignoresMouseEvents = true
+        self.panel = panel
+    }
+
+    private func fadeOut() {
+        guard let panel = panel else { return }
+        NSAnimationContext.runAnimationGroup({ context in
+            context.duration = 0.4
+            panel.animator().alphaValue = 0.0
+        }, completionHandler: { [weak self] in
+            self?.panel?.orderOut(nil)
+        })
+    }
+}