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>

Cargo.toml

@@ -40,6 +40,21 @@ notify-rust = { version = "4", optional = true }
 # System-tray icon (StatusNotifierItem over D-Bus). Pure-Rust, riding the same
 # zbus stack notify-rust already pulls — no GTK, no libappindicator/C libdbus.
 ksni = { version = "0.3", optional = true }
+# Hand-rolled windowing stack for the GUI (replaces eframe::run_native) so we
+# can drop the OS window on "hide to tray" — the only way to truly hide a
+# toplevel on Wayland — and recreate it on Show. All of these are already pulled
+# in transitively by eframe; making them direct adds no new crates to vet.
+# eframe is kept for its egui re-export + icon_data PNG decoder. egui_glow needs
+# its (non-default) `winit` feature for the `EguiGlow` integration type; eframe
+# pulls egui_glow but without that feature, so we enable it here.
+egui_glow = { version = "0.34.2", default-features = false, features = ["winit", "wayland", "x11"], optional = true }
+# winit's default set minus `wayland-csd-adwaita`: KWin (and most desktop
+# compositors) draw server-side decorations, and eframe never enabled CSD
+# either, so dropping it keeps the dependency tree identical to before (no
+# sctk-adwaita / tiny-skia / ttf-parser pulled in just for a fallback titlebar).
+winit = { version = "0.30", default-features = false, features = ["rwh_06", "x11", "wayland", "wayland-dlopen"], optional = true }
+glutin = { version = "0.32", optional = true }
+glutin-winit = { version = "0.5", optional = true }
 
 [profile.release]
 lto = "thin"
@@ -49,4 +64,4 @@ strip = "symbols"
 [features]
 # Opt-in graphical front-end (pixelpass --gui). Default-off so the headless
 # build never pulls the GUI toolkit tree.
-gui = ["dep:eframe", "dep:notify-rust", "dep:ksni"]
+gui = ["dep:eframe", "dep:notify-rust", "dep:ksni", "dep:egui_glow", "dep:winit", "dep:glutin", "dep:glutin-winit"]