feat(gui): hand-rolled winit loop for true window-hide on Wayland

Replace eframe::run_native with a winit ApplicationHandler + glutin +
egui_glow loop so "keep running in the tray" can genuinely hide the
window. winit's set_visible(false) is a deliberate no-op on Wayland
(xdg-shell has no unmap-but-keep-alive request), so the only way to hide
a toplevel is to destroy its surface: hide-to-tray now drops the Window +
GL surface (parking the GL context as not-current) and a tray click
recreates them and makes the context current again. The GL context,
glutin display/config, egui_glow painter (uploaded textures), and
egui-winit state (clipboard) all persist across the cycle — only the OS
window and its surface churn.

Wakeups route through winit's EventLoopProxy (the new Waker, and the
tray) instead of egui's repaint callback, so a child event or tray click
wakes the loop even while the window is dropped and no frame is running —
keeping viewer join/leave notifications and the tray tooltip live while
hidden. Removes the old Wayland minimize-to-tray fallback (window stayed
in the taskbar); hide is now uniform on Wayland and X11.

Deps: winit/glutin/glutin-winit/egui_glow promoted to direct (gui-gated,
optional) — all already transitive via eframe, so no new crates. winit's
default features minus wayland-csd-adwaita, so sctk-adwaita/tiny-skia/
ttf-parser aren't pulled for a CSD fallback titlebar (KWin draws
server-side decorations, and eframe never had CSD either).

Verified end-to-end on KWin Wayland: launch->render; close->window AND
taskbar entry gone (true hide, process stays alive); tray activate->
window + GL surface recreated and renders; tray quit->clean exit; stderr
clean throughout. cargo test --features gui: 15 pass; clippy clean;
headless dependency tree unchanged.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/gui/child.rs

@@ -12,11 +12,12 @@ use std::sync::mpsc::Receiver;
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
-use eframe::egui;
 use nix::sys::signal::{Signal, kill};
 use nix::unistd::Pid;
 use serde::Deserialize;
 
+use super::Waker;
+
 /// One parsed event from the child's stdout. Owned mirror of
 /// [`crate::common::output::Event`] (which borrows for emit); kept separate so
 /// the wire format and the parser can evolve independently.
@@ -77,9 +78,13 @@ pub struct ChildProc {
 }
 
 impl ChildProc {
-    /// Spawn `pixelpass <args>` as a child, wiring up the event reader. `ctx`
-    /// is repainted whenever an event arrives so the UI updates live.
-    pub fn spawn(args: &[String], ctx: egui::Context) -> std::io::Result<Self> {
+    /// Spawn `pixelpass <args>` as a child, wiring up the event reader. The
+    /// `waker` is pinged whenever an event arrives so the UI thread wakes to
+    /// drain it — this wakes the winit event loop directly (via an
+    /// `EventLoopProxy`), so it works even when the window is hidden to the tray
+    /// and no frames are running (egui's own repaint callback would not fire
+    /// repeatedly in that idle state — see [`super::Waker`]).
+    pub fn spawn(args: &[String], waker: Waker) -> std::io::Result<Self> {
         let exe = std::env::current_exe()?;
         let mut child = Command::new(exe)
             .args(args)
@@ -104,9 +109,14 @@ impl ChildProc {
                     if tx.send(ev).is_err() {
                         break; // app gone
                     }
-                    ctx.request_repaint();
+                    waker.wake();
                 }
             }
+            // stdout closed → the child has exited (player closed, connection
+            // ended, or a failed launch). Wake once more so the UI reaps it and
+            // clears the "running" view, even if no final event was emitted and
+            // the window is hidden to the tray.
+            waker.wake();
         });
 
         let stderr_tail = Arc::new(Mutex::new(Vec::<String>::new()));