feat(apprt-gtk): port the GTK4/libadwaita app runtime

Ports ZIG/src/apprt/gtk into ghostty-apprt-gtk: every GObject class
(application, window, tab, split tree, surface + scrolled window,
child-exited banner, search/key-state/resize overlays, command palette,
global shortcuts, all dialogs, config wrapper) as glib subclasses with
the same GType names, properties, signals and template children; GDK
key translation; X11 and Wayland window-protocol helpers (blur, CSD,
quick terminal via gtk4-layer-shell); single-instance D-Bus IPC;
gsettings; cgroup scope creation.

build.rs compiles Ghostty's blueprints with blueprint-compiler and
bundles UI, CSS and icons into a gresource, as Ghostty's build does.

The core is not ported yet, so the crate defines the boundary it needs
in src/core.rs (CoreApp, CoreSurface, RtApp, RtSurface, Waker); the
spec is in docs/rewrite/notes/ghostty-apprt-gtk.md. ghostty-core will
implement these traits (the crate no longer depends on core to avoid a
cycle). examples/demo.rs runs the app with a dummy core that clears the
GLArea; it launches on Wayland without GTK criticals.

Stubs/open items: toggle_visibility, float_window, secure_input and
close_all_windows return false; inspector is a no-op; X11/Wayland
protocol code is untested against real compositors; gtk4-rs doesn't
expose the GLArea framebuffer id, so the renderer must query it.

Also registers ghostty-apprt and ghostty-cli in workspace.dependencies.

Test Plan:
- cargo test -p ghostty-apprt-gtk (36 tests)
- DEMO_QUIT_AFTER_MS=3000 cargo run -p ghostty-apprt-gtk --example demo

crates/ghostty-apprt-gtk/Cargo.toml

@@ -3,11 +3,64 @@ name = "ghostty-apprt-gtk"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+build = "build.rs"
 
 [dependencies]
-ghostty-core.workspace = true
+ghostty-apprt.workspace = true
 ghostty-config.workspace = true
 ghostty-input.workspace = true
+ghostty-datastruct.workspace = true
+ghostty-os.workspace = true
+ghostty-vt.workspace = true
+log = "0.4"
+thiserror = "2"
+bitflags = "2"
+gtk = { package = "gtk4", version = "0.11", features = ["v4_14", "gnome_44"] }
+adw = { package = "libadwaita", version = "0.9", features = ["v1_5"] }
+gtk4-layer-shell = "0.8"
+gdk4-x11 = { version = "0.11.5", features = ["x11", "xlib"] }
+gdk4-wayland = { version = "0.11.5", features = ["wayland_crate"] }
+wayland-client = "0.31.15"
+wayland-protocols-plasma = { version = "0.3.12", features = ["client"] }
+wayland-protocols = { version = "0.32.13", features = ["client", "staging"] }
+wayland-backend = { version = "0.3.17", features = ["client_system"] }
+half = "2"
+libc = "0.2.190"
+signal-hook = "0.4.5"
+libloading = "0.9.0"
 
-[lints]
-workspace = true
+[build-dependencies]
+glib-build-tools = "0.22"
+
+[dev-dependencies]
+env_logger = "0.11"
+glow = "0.18"
+
+[lints.rust]
+unsafe_code = "deny"
+
+[lints.clippy]
+pedantic = { level = "warn", priority = -1 }
+todo = "warn"
+unwrap_used = "warn"
+cast_possible_truncation = "allow"
+cast_possible_wrap = "allow"
+cast_sign_loss = "allow"
+cast_precision_loss = "allow"
+cast_lossless = "allow"
+module_name_repetitions = "allow"
+too_many_lines = "allow"
+missing_errors_doc = "allow"
+missing_panics_doc = "allow"
+similar_names = "allow"
+struct_excessive_bools = "allow"
+fn_params_excessive_bools = "allow"
+match_same_arms = "allow"
+unreadable_literal = "allow"
+many_single_char_names = "allow"
+doc_markdown = "allow"
+must_use_candidate = "allow"
+return_self_not_must_use = "allow"
+used_underscore_binding = "allow"
+large_stack_arrays = "allow"
+inline_always = "allow"