feat(apple/input): desktop (absolute) mouse mode on macOS — remote-desktop sweep M1

Folds the parked client-side-cursor machinery (cursorMode auto/always/
never, hidden while disabled) into the cross-client mouse model:
MouseInputMode capture|desktop under DefaultsKey.mouseMode, picked in
Settings ▸ Keyboard & mouse (macOS), resolved at session start and
gated off on gamescope hosts (relative-only EIS).

Desktop model = the un-neutered absolute path with the SDL cursor
policy: pointer never disassociated (enters/leaves the stream freely),
monitor forwards letterboxed absolute positions, and the local cursor
hides only while over the view via an invisible-cursor rect (the
host's composited cursor is the one you see; AppKit manages the rect,
so no hide/unhide balancing). ⌘⇧C becomes ⌃⌥⇧M — the same chord as
the SDL clients — flipping the model live with an atomic
release/re-engage.

Verified: swift build + full test suites green (macOS arm64).

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

clients/apple/Sources/PunktfunkKit/Input/InputCapture.swift

@@ -110,11 +110,11 @@ public final class InputCapture {
     /// event itself is swallowed). Main queue.
     public var onToggleCapture: (() -> Void)?
 
-    /// Fired on ⌘⇧C (the client-side-cursor toggle — flips between the captured/disassociated
-    /// relative path and the visible-cursor absolute path; detected here, like ⌘⎋, so it works
-    /// regardless of the current capture state and the event itself is swallowed). macOS only;
-    /// the absolute-vs-relative forwarding lives entirely in StreamLayerView. Main queue.
-    public var onToggleCursor: (() -> Void)?
+    /// Fired on ⌃⌥⇧M (the mouse-model flip, capture ⇄ desktop — cross-client parity with the
+    /// SDL clients' Ctrl+Alt+Shift+M; detected here, like ⌘⎋, so it works regardless of the
+    /// current capture state and the event itself is swallowed). macOS only; the
+    /// absolute-vs-relative forwarding lives entirely in StreamLayerView. Main queue.
+    public var onToggleMouseMode: (() -> Void)?
 
     /// The cross-client combos (Windows/Linux parity: Ctrl+Alt+Shift+Q/D/S), fired from the macOS
     /// keyDown monitor only WHILE FORWARDING — that's the state in which the app's menu (which
@@ -245,13 +245,14 @@ public final class InputCapture {
                 self.onToggleCapture?()
                 return nil
             }
-            // ⌘⇧C toggles the client-side cursor (visible-cursor absolute path vs the
-            // captured relative path). keyCode 8 = kVK_ANSI_C; layout-independent so it
-            // fires the same on any keyboard. Suppress the C (latched like ⌘⎋'s Esc) so it
-            // doesn't type into the host, and swallow the event so it doesn't beep.
-            if event.keyCode == 8 /* C */, flags == [.command, .shift] {
-                self.suppressedVK = 0x43 // VK_C — the same physical C is en route via GC
-                self.onToggleCursor?()
+            // ⌃⌥⇧M flips the mouse model (capture ⇄ desktop — the SDL clients' identical
+            // chord). Detected in both capture states, like ⌘⎋, so the model can be set
+            // before engaging. keyCode 46 = kVK_ANSI_M; layout-independent. Suppress the M
+            // (latched like ⌘⎋'s Esc) so it doesn't type into the host, and swallow the
+            // event so it doesn't beep.
+            if event.keyCode == 46 /* M */, flags == [.control, .option, .shift] {
+                self.suppressedVK = 0x4D // VK_M — the same physical M is en route via GC
+                self.onToggleMouseMode?()
                 return nil
             }
             // The cross-client combos (Ctrl+Alt+Shift+Q/D/S — the same set every other

clients/apple/Sources/PunktfunkKit/Input/MouseInputMode.swift

@@ -0,0 +1,12 @@
+/// How a physical mouse drives the host — the cross-client mouse model (the SDL clients'
+/// `MouseMode` / `Settings::mouse_mode`, design/remote-desktop-sweep.md M1). Stored stringly
+/// under `DefaultsKey.mouseMode`.
+public enum MouseInputMode: String, CaseIterable, Sendable {
+    /// Pointer capture (disassociated, hidden cursor, relative deltas) — the game model,
+    /// and the default: the only cursor you see is the host's.
+    case capture
+    /// Absolute pointer, uncaptured: the cursor enters and leaves the stream freely and
+    /// motion is forwarded as absolute positions through the letterbox. The remote desktop
+    /// model. Requires a host injector with absolute support (not gamescope).
+    case desktop
+}