feat(client/input): desktop (absolute) mouse mode — remote-desktop sweep M1

New physical-mouse model beside capture: Desktop leaves the pointer
uncaptured and sends absolute positions through the letterbox
(MouseMoveAbs — every host injector already consumes it). Capture
stays the default and the game model.

- pf-client-core: MouseMode (capture|desktop) persisted in Settings,
  default capture so existing stores are unchanged.
- pf-presenter: Capture grows a desktop model — latest-wins pending
  abs position coalesced per loop iteration (same 1000 Hz discipline
  as relative), flushed before clicks/keys/wheel so they land where
  the cursor is; Ctrl+Alt+Shift+M flips the model live; local cursor
  stays hidden over the window (the host's composited cursor is the
  one you see until the M2 cursor channel); Windows keyboard grab
  only engages for capture (a desktop stream is something you
  Alt-Tab away from).
- gamescope gating: its EIS is relative-only, so desktop mode is
  pinned off there (resolved_compositor), with a log note.
- Settings surfaces: GTK row (dynamic caption), WinUI combo,
  console-UI row + step test, capture-hint line.

Verified: fmt + clippy -D warnings + tests (33/40/19) on Linux .21;
clippy -D warnings for all five crates incl. punktfunk-client-windows
native on .173.

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

crates/pf-client-core/src/trust.rs

@@ -456,6 +456,48 @@ impl TouchMode {
     }
 }
 
+/// How a physical mouse drives the host — the desktop-sweep mouse model
+/// (design/remote-desktop-sweep.md M1). Stored stringly in [`Settings::mouse_mode`] so the
+/// file stays readable; parsed with [`MouseMode::from_name`].
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum MouseMode {
+    /// Pointer lock (relative deltas, hidden cursor) — the game model, and the default:
+    /// the only cursor you see is the host's.
+    Capture,
+    /// Absolute pointer, uncaptured: the cursor enters and leaves the stream freely and
+    /// motion goes on the wire as absolute positions through the letterbox. The remote
+    /// desktop model. Requires a host injector with absolute support (not gamescope).
+    Desktop,
+}
+
+impl MouseMode {
+    /// Cycle/picker order (also the settings pickers' option order).
+    pub const ALL: [MouseMode; 2] = [MouseMode::Capture, MouseMode::Desktop];
+
+    /// Parse the persisted name, defaulting to `Capture` for unset/unknown values.
+    pub fn from_name(s: &str) -> MouseMode {
+        match s {
+            "desktop" => MouseMode::Desktop,
+            _ => MouseMode::Capture,
+        }
+    }
+
+    /// The persisted name (the inverse of [`from_name`](Self::from_name)).
+    pub fn as_name(self) -> &'static str {
+        match self {
+            MouseMode::Capture => "capture",
+            MouseMode::Desktop => "desktop",
+        }
+    }
+
+    pub fn label(self) -> &'static str {
+        match self {
+            MouseMode::Capture => "Capture (games)",
+            MouseMode::Desktop => "Desktop (absolute)",
+        }
+    }
+}
+
 /// App settings, persisted as JSON. Stringly-typed gamepad/compositor prefs so the file
 /// stays readable; parsed with `*Pref::from_name` at connect time.
 #[derive(Clone, Serialize, Deserialize)]
@@ -490,6 +532,12 @@ pub struct Settings {
     /// stores load as trackpad.
     #[serde(default = "default_touch_mode")]
     pub touch_mode: String,
+    /// How a physical mouse drives the host: a [`MouseMode`] name — `"capture"` (default,
+    /// pointer lock + relative) or `"desktop"` (uncaptured absolute pointer). Read at
+    /// connect via [`Settings::mouse_mode`]. `default` so pre-existing stores load as
+    /// capture — today's behavior.
+    #[serde(default = "default_mouse_mode")]
+    pub mouse_mode: String,
     /// Grab compositor shortcuts (Alt+Tab, Super…) while input is captured.
     pub inhibit_shortcuts: bool,
     /// Stream the default microphone to the host's virtual mic source.
@@ -577,6 +625,10 @@ fn default_touch_mode() -> String {
     "trackpad".into()
 }
 
+fn default_mouse_mode() -> String {
+    "capture".into()
+}
+
 fn default_true() -> bool {
     true
 }
@@ -604,6 +656,10 @@ impl Settings {
         TouchMode::from_name(&self.touch_mode)
     }
 
+    pub fn mouse_mode(&self) -> MouseMode {
+        MouseMode::from_name(&self.mouse_mode)
+    }
+
     /// The `codec` setting as a `quic::CODEC_*` preference bit (`0` = auto).
     pub fn preferred_codec(&self) -> u8 {
         match self.codec.as_str() {
@@ -631,6 +687,7 @@ impl Default for Settings {
             forward_pad: String::new(),
             compositor: "auto".into(),
             touch_mode: "trackpad".into(),
+            mouse_mode: "capture".into(),
             inhibit_shortcuts: true,
             mic_enabled: false,
             audio_channels: 2,