feat(core): port App/Surface and wire up the runnable ghostty binary

This is the integration step that turns the ported crates into a working
terminal: `cargo run` now opens a GTK window running the user's shell.

ghostty-core ports App.zig, Surface.zig (split into keyboard, mouse,
binding, clipboard and config submodules), surface_mouse.zig and
global.zig, and implements the runtime traits. perform_binding_action
handles every binding action.

Cross-crate integration:
- The core<->runtime traits (CoreApp, CoreSurface, RtApp, RtSurface,
  Waker) move from apprt-gtk into ghostty_apprt::runtime_api so the core
  stays runtime-agnostic; Scrollbar/RendererHealth stand-ins are replaced
  by the real terminal/renderer types.
- termio now uses ghostty_renderer::state::{State, SharedState}; the
  renderer calls kitty_update; image-storage-limit is applied at init
  and on config change.
- The search thread locks the terminal through a TerminalLock trait so
  it can share the render state mutex; termio's Wakeup gained a hook to
  wake the renderer thread.
- apprt-gtk: GL proc addresses are resolved through libepoxy's
  epoxy_glFoo pointer variables (plain glFoo symbols resolved to null),
  default DPI fixed to 96, libadwaita version read without GTK init so
  --version works headless.

The root binary dispatches +actions to ghostty-cli (list-fonts,
show-face and new-window are now wired) and otherwise runs the GTK app
with the real core.

Verified at runtime on Wayland and X11: shell prompt and colored output
render, child exit closes the window cleanly. Not yet verified: keyboard
and mouse input, clipboard, IME, tabs and splits (no key injection was
possible in this environment). GHOSTTY_DEBUG_SCREENSHOT=<png> dumps the
renderer's last frame for headless checks.

Test Plan:
- cargo test --workspace (2890 passed)
- cargo clippy --workspace --all-targets -- -D warnings
- GSETTINGS_BACKEND=memory GHOSTTY_RESOURCES_DIR=/usr/share/ghostty \
  cargo run

crates/ghostty-termio/src/exec.rs

@@ -40,7 +40,7 @@ use crate::command::{
 use crate::pty::{self, Mode, Pty, Winsize};
 use crate::shell_integration::{self, EnvMap, Shell};
 use crate::sinks::SurfaceMailbox;
-use crate::state::RendererState;
+use crate::state::{SharedState, SharedStateExt};
 use crate::termio::Output;
 use crate::wakeup::Wakeup;
 use ghostty_apprt::surface::{ChildExited, Message as SurfaceMessage};
@@ -192,7 +192,7 @@ impl Exec {
         &mut self,
         output: Arc<Output>,
         surface_mailbox: Arc<dyn SurfaceMailbox>,
-        renderer_state: Arc<RendererState>,
+        renderer_state: SharedState,
     ) -> Result<ThreadData, Error> {
         // Start our subprocess
         let (read_fd, write_fd) = self.subprocess.start()?;
@@ -382,7 +382,7 @@ pub struct ThreadData {
     termios_mode: Mode,
 
     surface_mailbox: Arc<dyn SurfaceMailbox>,
-    renderer_state: Arc<RendererState>,
+    renderer_state: SharedState,
 }
 
 impl ThreadData {
@@ -579,7 +579,7 @@ impl ThreadData {
             // If our password input state changed on the terminal then
             // we notify the surface.
             let changed = {
-                let t = self.renderer_state.lock();
+                let t = self.renderer_state.lock_terminal();
                 t.flags.password_input != password_input
             };