fix: hide + freeze the local cursor while streaming

The host renders its own cursor from our raw deltas, so the local macOS cursor both
stays visible and drifts away from the remote one — and it can wander out of the window,
where a click focuses another app. While the stream has focus, do what Moonlight does:
warp the cursor mid-view, disconnect it from mouse movement
(CGAssociateMouseAndMouseCursorPosition(false) — GCMouse still delivers raw HID deltas),
and hide it. Released on app deactivation (Cmd+Tab is the escape hatch), view teardown,
and disconnect; re-captured when the stream regains focus. The HUD's Disconnect gains ⌘D
since a hidden, frozen cursor can't click it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkKit/StreamView.swift

@@ -9,9 +9,39 @@
 // UIViewRepresentable.
 
 #if os(macOS)
+import AppKit
 import AVFoundation
 import SwiftUI
 
+/// Hides the LOCAL cursor while streaming. The host renders its own cursor, and the local
+/// one both diverges from it (the host applies acceleration/clamping to our raw deltas)
+/// and can wander out of the window — a click there would focus another app. So while the
+/// stream has focus we do what Moonlight does: warp the cursor into the view, freeze it
+/// (`CGAssociateMouseAndMouseCursorPosition(false)` — GCMouse still delivers raw HID
+/// deltas), and hide it. hide/unhide and associate are balanced via `captured`.
+private final class CursorCapture {
+    private var captured = false
+
+    func capture(in view: NSView) {
+        guard !captured, let window = view.window, view.bounds.width > 0 else { return }
+        // Park the cursor mid-view so a click can't land in (and activate) another app.
+        let rectOnScreen = window.convertToScreen(view.convert(view.bounds, to: nil))
+        let primaryHeight = NSScreen.screens.first?.frame.height ?? 0
+        CGWarpMouseCursorPosition(
+            CGPoint(x: rectOnScreen.midX, y: primaryHeight - rectOnScreen.midY))
+        CGAssociateMouseAndMouseCursorPosition(0)
+        NSCursor.hide()
+        captured = true
+    }
+
+    func release() {
+        guard captured else { return }
+        CGAssociateMouseAndMouseCursorPosition(1)
+        NSCursor.unhide()
+        captured = false
+    }
+}
+
 public struct StreamView: NSViewRepresentable {
     private let connection: PunktfunkConnection
     private let onFrame: (@Sendable (AccessUnit) -> Void)?
@@ -68,16 +98,44 @@ public final class StreamLayerView: NSView {
     private let displayLayer = AVSampleBufferDisplayLayer()
     private var token: PumpToken?
     public private(set) var connection: PunktfunkConnection?
+    private let cursorCapture = CursorCapture()
+    private var appObservers: [NSObjectProtocol] = []
 
     public override init(frame: NSRect) {
         super.init(frame: frame)
         displayLayer.videoGravity = .resizeAspect
         layer = displayLayer // layer-hosting: assign before wantsLayer
         wantsLayer = true
+        // The cursor comes back whenever the app loses focus (Cmd+Tab is the escape
+        // hatch) and is re-captured when the stream regains it.
+        appObservers.append(NotificationCenter.default.addObserver(
+            forName: NSApplication.didResignActiveNotification, object: nil, queue: .main
+        ) { [weak self] _ in
+            self?.cursorCapture.release()
+        })
+        appObservers.append(NotificationCenter.default.addObserver(
+            forName: NSApplication.didBecomeActiveNotification, object: nil, queue: .main
+        ) { [weak self] _ in
+            self?.captureCursorIfStreaming()
+        })
     }
 
     public required init?(coder: NSCoder) { fatalError("not used") }
 
+    public override func viewDidMoveToWindow() {
+        super.viewDidMoveToWindow()
+        if window == nil {
+            cursorCapture.release()
+        } else {
+            captureCursorIfStreaming()
+        }
+    }
+
+    private func captureCursorIfStreaming() {
+        guard token != nil, NSApp.isActive else { return }
+        cursorCapture.capture(in: self)
+    }
+
     /// Pump thread: pull AUs from the connection, wrap, enqueue. The first IDR yields the
     /// format description; non-IDR AUs before it are dropped (the host opens with an IDR).
     public func start(
@@ -126,17 +184,20 @@ public final class StreamLayerView: NSView {
         thread.name = "punktfunk-pump"
         thread.qualityOfService = .userInteractive
         thread.start()
+        captureCursorIfStreaming()
     }
 
     /// Stop pumping (≤ one poll timeout). Does not close the connection — that stays with
     /// whoever owns it (PunktfunkConnection.close() is safe alongside a draining pump).
     public func stop() {
+        cursorCapture.release()
         token?.cancel()
         token = nil
         connection = nil
     }
 
     deinit {
+        appObservers.forEach(NotificationCenter.default.removeObserver(_:))
         token?.cancel()
     }
 }