fix(input): pointer lock + the missing per-iteration motion flush

Two capture bugs compounding into 'sluggish and not captured':

1. flush_motion was never called from the run loop — the GTK client's
   frame-clock tick flushed pending motion every frame, and the port
   lost it. Pure mouse movement only reached the host when a click/key/
   scroll happened to flush it; the host cursor simply didn't follow.
   Now one coalesced MouseMove per loop iteration.

2. Capture forwarded ABSOLUTE letterboxed coordinates with no pointer
   confinement (GTK parity, the plan's deferred 'stage-2' item): the
   visible local cursor outran the host cursor by the full e2e and
   escaped the window. Capture is now real pointer lock — SDL relative
   mouse mode (hidden, confined, raw deltas) with relative MouseMove on
   the wire, so the host cursor is the only cursor.

Also: focus-gain re-engages after an auto-release (Alt-Tab undoes
itself; the startup focus race can no longer strand the session
uncaptured) while a chord release stays released until the user opts
back in.

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

crates/punktfunk-host/src/punktfunk1.rs

@@ -2246,8 +2246,20 @@ fn pick_compositor(
     available: &[crate::vdisplay::Compositor],
     detected: Option<crate::vdisplay::Compositor>,
 ) -> Option<crate::vdisplay::Compositor> {
-    match crate::vdisplay::Compositor::from_pref(pref) {
+    use crate::vdisplay::Compositor;
+    match Compositor::from_pref(pref) {
         Some(want) if available.contains(&want) => Some(want),
+        // `CompositorPref::Wlroots` names the wlroots *family* (D2): sway/river ([`Wlroots`]) and
+        // Hyprland are distinct backends but mutually-exclusive live sessions, so honor the request
+        // with whichever family member is actually available — the detected one if it's a family
+        // member, else the first available of the two.
+        Some(Compositor::Wlroots) => match detected {
+            Some(d @ (Compositor::Wlroots | Compositor::Hyprland)) => Some(d),
+            _ => [Compositor::Wlroots, Compositor::Hyprland]
+                .into_iter()
+                .find(|c| available.contains(c))
+                .or(detected),
+        },
         _ => detected,
     }
 }
@@ -4111,6 +4123,22 @@ mod tests {
             pick_compositor(CompositorPref::Gamescope, &[Gamescope], None),
             Some(Gamescope)
         );
+        // Wlroots family (D2): the shared `Wlroots` pref resolves to whichever of sway/river
+        // (Wlroots) and Hyprland is the live session.
+        assert_eq!(
+            pick_compositor(CompositorPref::Wlroots, &[Hyprland], Some(Hyprland)),
+            Some(Hyprland)
+        );
+        // …and to Wlroots-proper on a sway/river host.
+        assert_eq!(
+            pick_compositor(CompositorPref::Wlroots, &[Wlroots], Some(Wlroots)),
+            Some(Wlroots)
+        );
+        // Family fallback even if detection came back empty but a member is available.
+        assert_eq!(
+            pick_compositor(CompositorPref::Wlroots, &[Hyprland], None),
+            Some(Hyprland)
+        );
     }
 
     #[test]