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

Cargo.lock

@@ -1208,6 +1208,8 @@ dependencies = [
  "ghostty-config",
  "ghostty-datastruct",
  "ghostty-input",
+ "ghostty-renderer",
+ "ghostty-terminal",
  "ghostty-vt",
  "thiserror 2.0.21",
 ]
@@ -1248,7 +1250,9 @@ name = "ghostty-cli"
 version = "0.1.0"
 dependencies = [
  "flate2",
+ "ghostty-apprt",
  "ghostty-config",
+ "ghostty-font",
  "ghostty-input",
  "ghostty-os",
  "log",
@@ -1275,6 +1279,9 @@ dependencies = [
 name = "ghostty-core"
 version = "0.1.0"
 dependencies = [
+ "base64 0.23.1",
+ "crossbeam-channel",
+ "ghostty-apprt",
  "ghostty-config",
  "ghostty-datastruct",
  "ghostty-font",
@@ -1283,6 +1290,12 @@ dependencies = [
  "ghostty-renderer",
  "ghostty-terminal",
  "ghostty-termio",
+ "ghostty-unicode",
+ "ghostty-vt",
+ "log",
+ "onig",
+ "png",
+ "thiserror 2.0.21",
 ]
 
 [[package]]
@@ -1361,9 +1374,12 @@ dependencies = [
 name = "ghostty-rs"
 version = "0.1.0"
 dependencies = [
+ "ghostty-apprt",
  "ghostty-apprt-gtk",
+ "ghostty-cli",
  "ghostty-config",
  "ghostty-core",
+ "log",
 ]
 
 [[package]]